src/problems.c

   1 /*
   2  * Copyright (c) 2007-2009, Novell Inc.
   3  *
   4  * This program is licensed under the BSD license, read LICENSE.BSD
   5  * for further information
   6  */
   7
   8 /*
   9  * problems.c
  10  *
  11  */
  12
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <unistd.h>
  16 #include <string.h>
  17 #include <assert.h>
  18
  19 #include "solver.h"
  20 #include "solver_private.h"
  21 #include "bitmap.h"
  22 #include "pool.h"
  23 #include "util.h"
  24 #include "evr.h"
  25 #include "solverdebug.h"
  26
  27
  28 /**********************************************************************************/
  29
  30 /* a problem is an item on the solver's problem list. It can either be >0, in that
  31  * case it is a update/infarch/dup rule, or it can be <0, which makes it refer to a job
  32  * consisting of multiple job rules.
  33  */
  34
  35 void
  36 solver_disableproblem(Solver *solv, Id v)
  37 {
  38   Rule *r;
  39   int i;
  40   Id *jp;
  41
  42   if (v > 0)
  43     {
  44       if (v >= solv->infarchrules && v < solv->infarchrules_end)
  45         {
  46           Pool *pool = solv->pool;
  47           Id name = pool->solvables[-solv->rules[v].p].name;
  48           while (v > solv->infarchrules && pool->solvables[-solv->rules[v - 1].p].name == name)
  49             v--;
  50           for (; v < solv->infarchrules_end && pool->solvables[-solv->rules[v].p].name == name; v++)
  51             solver_disablerule(solv, solv->rules + v);
  52           return;
  53         }
  54       if (v >= solv->duprules && v < solv->duprules_end)
  55         {
  56           Pool *pool = solv->pool;
  57           Id name = pool->solvables[-solv->rules[v].p].name;
  58           while (v > solv->duprules && pool->solvables[-solv->rules[v - 1].p].name == name)
  59             v--;
  60           for (; v < solv->duprules_end && pool->solvables[-solv->rules[v].p].name == name; v++)
  61             solver_disablerule(solv, solv->rules + v);
  62           return;
  63         }
  64       solver_disablerule(solv, solv->rules + v);
  65 #if 0
  66       /* XXX: doesn't work */
  67       if (v >= solv->updaterules && v < solv->updaterules_end)
  68         {
  69           /* enable feature rule if we disabled the update rule */
  70           r = solv->rules + (v - solv->updaterules + solv->featurerules);
  71           if (r->p)
  72             solver_enablerule(solv, r);
  73         }
  74 #endif
  75       return;
  76     }
  77   v = -(v + 1);
  78   jp = solv->ruletojob.elements;
  79   for (i = solv->jobrules, r = solv->rules + i; i < solv->jobrules_end; i++, r++, jp++)
  80     if (*jp == v)
  81       solver_disablerule(solv, r);
  82 }
  83
  84 /*-------------------------------------------------------------------
  85  * enableproblem
  86  */
  87
  88 void
  89 solver_enableproblem(Solver *solv, Id v)
  90 {
  91   Rule *r;
  92   int i;
  93   Id *jp;
  94
  95   if (v > 0)
  96     {
  97       if (v >= solv->infarchrules && v < solv->infarchrules_end)
  98         {
  99           Pool *pool = solv->pool;
 100           Id name = pool->solvables[-solv->rules[v].p].name;
 101           while (v > solv->infarchrules && pool->solvables[-solv->rules[v - 1].p].name == name)
 102             v--;
 103           for (; v < solv->infarchrules_end && pool->solvables[-solv->rules[v].p].name == name; v++)
 104             solver_enablerule(solv, solv->rules + v);
 105           return;
 106         }
 107       if (v >= solv->duprules && v < solv->duprules_end)
 108         {
 109           Pool *pool = solv->pool;
 110           Id name = pool->solvables[-solv->rules[v].p].name;
 111           while (v > solv->duprules && pool->solvables[-solv->rules[v - 1].p].name == name)
 112             v--;
 113           for (; v < solv->duprules_end && pool->solvables[-solv->rules[v].p].name == name; v++)
 114             solver_enablerule(solv, solv->rules + v);
 115           return;
 116         }
 117       if (v >= solv->featurerules && v < solv->featurerules_end)
 118         {
 119           /* do not enable feature rule if update rule is enabled */
 120           r = solv->rules + (v - solv->featurerules + solv->updaterules);
 121           if (r->d >= 0)
 122             return;
 123         }
 124       solver_enablerule(solv, solv->rules + v);
 125       if (v >= solv->updaterules && v < solv->updaterules_end)
 126         {
 127           /* disable feature rule when enabling update rule */
 128           r = solv->rules + (v - solv->updaterules + solv->featurerules);
 129           if (r->p)
 130             solver_disablerule(solv, r);
 131         }
 132       return;
 133     }
 134   v = -(v + 1);
 135   jp = solv->ruletojob.elements;
 136   for (i = solv->jobrules, r = solv->rules + i; i < solv->jobrules_end; i++, r++, jp++)
 137     if (*jp == v)
 138       solver_enablerule(solv, r);
 139 }
 140
 141
 142 /*-------------------------------------------------------------------
 143  * enable weak rules
 144  *
 145  * Reenable all disabled weak rules (marked in weakrulemap)
 146  *
 147  */
 148
 149 static void
 150 enableweakrules(Solver *solv)
 151 {
 152   int i;
 153   Rule *r;
 154
 155   if (!solv->weakrulemap.size)
 156     return;
 157   for (i = 1, r = solv->rules + i; i < solv->learntrules; i++, r++)
 158     {
 159       if (r->d >= 0) /* already enabled? */
 160         continue;
 161       if (!MAPTST(&solv->weakrulemap, i))
 162         continue;
 163       solver_enablerule(solv, r);
 164     }
 165   /* make sure broken orphan rules stay disabled */
 166   if (solv->brokenorphanrules)
 167     for (i = 0; i < solv->brokenorphanrules->count; i++)
 168       solver_disablerule(solv, solv->rules + solv->brokenorphanrules->elements[i]);
 169 }
 170
 171
 172 /*-------------------------------------------------------------------
 173  *
 174  * refine_suggestion
 175  *
 176  * at this point, all rules that led to conflicts are disabled.
 177  * we re-enable all rules of a problem set but rule "sug", then
 178  * continue to disable more rules until there as again a solution.
 179  */
 180
 181 /* FIXME: think about conflicting assertions */
 182
 183 static void
 184 refine_suggestion(Solver *solv, Id *problem, Id sug, Queue *refined, int essentialok)
 185 {
 186   Pool *pool = solv->pool;
 187   int i, j;
 188   Id v;
 189   Queue disabled;
 190   int disabledcnt;
 191
 192   IF_POOLDEBUG (SOLV_DEBUG_SOLUTIONS)
 193     {
 194       POOL_DEBUG(SOLV_DEBUG_SOLUTIONS, "refine_suggestion start\n");
 195       for (i = 0; problem[i]; i++)
 196         {
 197           if (problem[i] == sug)
 198             POOL_DEBUG(SOLV_DEBUG_SOLUTIONS, "=> ");
 199           solver_printproblem(solv, problem[i]);
 200         }
 201     }
 202   queue_empty(refined);
 203   if (!essentialok && sug < 0 && (solv->job.elements[-sug - 1] & SOLVER_ESSENTIAL) != 0)
 204     return;
 205   queue_init(&disabled);
 206   queue_push(refined, sug);
 207
 208   /* re-enable all problem rules with the exception of "sug"(gestion) */
 209   solver_reset(solv);
 210
 211   for (i = 0; problem[i]; i++)
 212     if (problem[i] != sug)
 213       solver_enableproblem(solv, problem[i]);
 214
 215   if (sug < 0)
 216     solver_reenablepolicyrules(solv, -sug);
 217   else if (sug >= solv->updaterules && sug < solv->updaterules_end)
 218     {
 219       /* enable feature rule */
 220       Rule *r = solv->rules + solv->featurerules + (sug - solv->updaterules);
 221       if (r->p)
 222         solver_enablerule(solv, r);
 223     }
 224
 225   enableweakrules(solv);
 226
 227   for (;;)
 228     {
 229       int njob, nfeature, nupdate, pass;
 230       queue_empty(&solv->problems);
 231       solver_reset(solv);
 232       solver_run_sat(solv, 0, 0);
 233
 234       if (!solv->problems.count)
 235         {
 236           POOL_DEBUG(SOLV_DEBUG_SOLUTIONS, "no more problems!\n");
 237           break;                /* great, no more problems */
 238         }
 239       disabledcnt = disabled.count;
 240       /* start with 1 to skip over proof index */
 241       njob = nfeature = nupdate = 0;
 242       for (pass = 0; pass < 2; pass++)
 243         {
 244           for (i = 1; i < solv->problems.count - 1; i++)
 245             {
 246               /* ignore solutions in refined */
 247               v = solv->problems.elements[i];
 248               if (v == 0)
 249                 break;  /* end of problem reached */
 250               if (sug != v)
 251                 {
 252                   /* check if v is in the given problems list
 253                    * we allow disabling all problem rules *after* sug in
 254                    * pass 2, to prevent getting the same solution twice */
 255                   for (j = 0; problem[j]; j++)
 256                     if (problem[j] == v || (pass && problem[j] == sug))
 257                       break;
 258                   if (problem[j] == v)
 259                     continue;
 260                 }
 261               if (v >= solv->featurerules && v < solv->featurerules_end)
 262                 nfeature++;
 263               else if (v > 0)
 264                 nupdate++;
 265               else
 266                 {
 267                   if (!essentialok && (solv->job.elements[-v - 1] & SOLVER_ESSENTIAL) != 0)
 268                     continue;   /* not that one! */
 269                   njob++;
 270                 }
 271               queue_push(&disabled, v);
 272             }
 273           if (disabled.count != disabledcnt)
 274             break;
 275         }
 276       if (disabled.count == disabledcnt)
 277         {
 278           /* no solution found, this was an invalid suggestion! */
 279           POOL_DEBUG(SOLV_DEBUG_SOLUTIONS, "no solution found!\n");
 280           refined->count = 0;
 281           break;
 282         }
 283       if (!njob && nupdate && nfeature)
 284         {
 285           /* got only update rules, filter out feature rules */
 286           POOL_DEBUG(SOLV_DEBUG_SOLUTIONS, "throwing away feature rules\n");
 287           for (i = j = disabledcnt; i < disabled.count; i++)
 288             {
 289               v = disabled.elements[i];
 290               if (v < solv->featurerules || v >= solv->featurerules_end)
 291                 disabled.elements[j++] = v;
 292             }
 293           disabled.count = j;
 294           nfeature = 0;
 295         }
 296       if (disabled.count == disabledcnt + 1)
 297         {
 298           /* just one suggestion, add it to refined list */
 299           v = disabled.elements[disabledcnt];
 300           if (!nfeature && v != sug)
 301             queue_push(refined, v);     /* do not record feature rules */
 302           solver_disableproblem(solv, v);
 303           if (v >= solv->updaterules && v < solv->updaterules_end)
 304             {
 305               Rule *r = solv->rules + (v - solv->updaterules + solv->featurerules);
 306               if (r->p)
 307                 solver_enablerule(solv, r);     /* enable corresponding feature rule */
 308             }
 309           if (v < 0)
 310             solver_reenablepolicyrules(solv, -v);
 311         }
 312       else
 313         {
 314           /* more than one solution, disable all */
 315           /* do not push anything on refine list, as we do not know which solution to choose */
 316           /* thus, the user will get another problem if he selects this solution, where he
 317            * can choose the right one */
 318           IF_POOLDEBUG (SOLV_DEBUG_SOLUTIONS)
 319             {
 320               POOL_DEBUG(SOLV_DEBUG_SOLUTIONS, "more than one solution found:\n");
 321               for (i = disabledcnt; i < disabled.count; i++)
 322                 solver_printproblem(solv, disabled.elements[i]);
 323             }
 324           for (i = disabledcnt; i < disabled.count; i++)
 325             {
 326               v = disabled.elements[i];
 327               solver_disableproblem(solv, v);
 328               if (v >= solv->updaterules && v < solv->updaterules_end)
 329                 {
 330                   Rule *r = solv->rules + (v - solv->updaterules + solv->featurerules);
 331                   if (r->p)
 332                     solver_enablerule(solv, r);
 333                 }
 334             }
 335         }
 336     }
 337   /* all done, get us back into the same state as before */
 338   /* enable refined rules again */
 339   for (i = 0; i < disabled.count; i++)
 340     solver_enableproblem(solv, disabled.elements[i]);
 341   queue_free(&disabled);
 342   /* reset policy rules */
 343   for (i = 0; problem[i]; i++)
 344     solver_enableproblem(solv, problem[i]);
 345   solver_disablepolicyrules(solv);
 346   /* disable problem rules again */
 347   for (i = 0; problem[i]; i++)
 348     solver_disableproblem(solv, problem[i]);
 349   POOL_DEBUG(SOLV_DEBUG_SOLUTIONS, "refine_suggestion end\n");
 350 }
 351
 352
 353 /*-------------------------------------------------------------------
 354  * sorting helper for problems
 355  *
 356  * bring update rules before job rules
 357  * make essential job rules last
 358  */
 359
 360 static int
 361 problems_sortcmp(const void *ap, const void *bp, void *dp)
 362 {
 363   Queue *job = dp;
 364   Id a = *(Id *)ap, b = *(Id *)bp;
 365   if (a < 0 && b > 0)
 366     return 1;
 367   if (a > 0 && b < 0)
 368     return -1;
 369   if (a < 0 && b < 0)
 370     {
 371       int af = job->elements[-a - 1] & SOLVER_ESSENTIAL;
 372       int bf = job->elements[-b - 1] & SOLVER_ESSENTIAL;
 373       int x = af - bf;
 374       if (x)
 375         return x;
 376     }
 377   return a - b;
 378 }
 379
 380 /*
 381  * convert a solution rule into a job modifier
 382  */
 383 static void
 384 convertsolution(Solver *solv, Id why, Queue *solutionq)
 385 {
 386   Pool *pool = solv->pool;
 387   if (why < 0)
 388     {
 389       why = -why;
 390       if (why < solv->pooljobcnt)
 391         {
 392           queue_push(solutionq, SOLVER_SOLUTION_POOLJOB);
 393           queue_push(solutionq, why);
 394         }
 395       else
 396         {
 397           queue_push(solutionq, SOLVER_SOLUTION_JOB);
 398           queue_push(solutionq, why - solv->pooljobcnt);
 399         }
 400       return;
 401     }
 402   if (why >= solv->infarchrules && why < solv->infarchrules_end)
 403     {
 404       Id p, name;
 405       /* infarch rule, find replacement */
 406       assert(solv->rules[why].p < 0);
 407       name = pool->solvables[-solv->rules[why].p].name;
 408       while (why > solv->infarchrules && pool->solvables[-solv->rules[why - 1].p].name == name)
 409         why--;
 410       p = 0;
 411       for (; why < solv->infarchrules_end && pool->solvables[-solv->rules[why].p].name == name; why++)
 412         if (solv->decisionmap[-solv->rules[why].p] > 0)
 413           {
 414             p = -solv->rules[why].p;
 415             break;
 416           }
 417       if (!p)
 418         return;         /* false alarm */
 419       queue_push(solutionq, SOLVER_SOLUTION_INFARCH);
 420       queue_push(solutionq, p);
 421       return;
 422     }
 423   if (why >= solv->duprules && why < solv->duprules_end)
 424     {
 425       Id p, name;
 426       /* dist upgrade rule, find replacement */
 427       assert(solv->rules[why].p < 0);
 428       name = pool->solvables[-solv->rules[why].p].name;
 429       while (why > solv->duprules && pool->solvables[-solv->rules[why - 1].p].name == name)
 430         why--;
 431       p = 0;
 432       for (; why < solv->duprules_end && pool->solvables[-solv->rules[why].p].name == name; why++)
 433         if (solv->decisionmap[-solv->rules[why].p] > 0)
 434           {
 435             p = -solv->rules[why].p;
 436             break;
 437           }
 438       if (!p)
 439         return;         /* false alarm */
 440       queue_push(solutionq, SOLVER_SOLUTION_DISTUPGRADE);
 441       queue_push(solutionq, p);
 442       return;
 443     }
 444   if (why >= solv->updaterules && why < solv->updaterules_end)
 445     {
 446       /* update rule, find replacement package */
 447       Id p, pp, rp = 0;
 448       Rule *rr;
 449
 450       /* check if this is a false positive, i.e. the update rule is fulfilled */
 451       rr = solv->rules + why;
 452       FOR_RULELITERALS(p, pp, rr)
 453         if (p > 0 && solv->decisionmap[p] > 0)
 454           return;       /* false alarm */
 455
 456       p = solv->installed->start + (why - solv->updaterules);
 457       if (solv->dupmap_all && solv->rules[why].p != p && solv->decisionmap[p] > 0)
 458         {
 459           /* distupgrade case, allow to keep old package */
 460           queue_push(solutionq, SOLVER_SOLUTION_DISTUPGRADE);
 461           queue_push(solutionq, p);
 462           return;
 463         }
 464       if (solv->decisionmap[p] > 0)
 465         return;         /* false alarm, turned out we can keep the package */
 466       rr = solv->rules + solv->featurerules + (why - solv->updaterules);
 467       if (!rr->p)
 468         rr = solv->rules + why;
 469       if (rr->w2)
 470         {
 471           int mvrp = 0;         /* multi-version replacement */
 472           FOR_RULELITERALS(rp, pp, rr)
 473             {
 474               if (rp > 0 && solv->decisionmap[rp] > 0 && pool->solvables[rp].repo != solv->installed)
 475                 {
 476                   mvrp = rp;
 477                   if (!(solv->multiversion.size && MAPTST(&solv->multiversion, rp)))
 478                     break;
 479                 }
 480             }
 481           if (!rp && mvrp)
 482             {
 483               /* found only multi-version replacements */
 484               /* have to split solution into two parts */
 485               queue_push(solutionq, p);
 486               queue_push(solutionq, mvrp);
 487             }
 488         }
 489       queue_push(solutionq, p);
 490       queue_push(solutionq, rp);
 491       return;
 492     }
 493   if (why >= solv->bestrules && why < solv->bestrules_end)
 494     {
 495       int mvrp;
 496       Id p, pp, rp = 0;
 497       Rule *rr;
 498       /* check false positive */
 499       rr = solv->rules + why;
 500       FOR_RULELITERALS(p, pp, rr)
 501         if (p > 0 && solv->decisionmap[p] > 0)
 502           return;       /* false alarm */
 503       /* check update/feature rule */
 504       p = solv->bestrules_pkg[why - solv->bestrules];
 505       if (p < 0)
 506         {
 507           /* install job */
 508           queue_push(solutionq, 0);
 509           queue_push(solutionq, solv->ruletojob.elements[-p - solv->jobrules] + 1);
 510           return;
 511         }
 512       if (solv->decisionmap[p] > 0)
 513         {
 514           /* disable best rule by keeping the old package */
 515           queue_push(solutionq, SOLVER_SOLUTION_BEST);
 516           queue_push(solutionq, p);
 517           return;
 518         }
 519       rr = solv->rules + solv->featurerules + (p - solv->installed->start);
 520       if (!rr->p)
 521         rr = solv->rules + solv->updaterules + (p - solv->installed->start);
 522       mvrp = 0;         /* multi-version replacement */
 523       FOR_RULELITERALS(rp, pp, rr)
 524         if (rp > 0 && solv->decisionmap[rp] > 0 && pool->solvables[rp].repo != solv->installed)
 525           {
 526             mvrp = rp;
 527             if (!(solv->multiversion.size && MAPTST(&solv->multiversion, rp)))
 528               break;
 529           }
 530       if (!rp && mvrp)
 531         {
 532           queue_push(solutionq, SOLVER_SOLUTION_BEST);  /* split, see above */
 533           queue_push(solutionq, mvrp);
 534           queue_push(solutionq, p);
 535           queue_push(solutionq, 0);
 536           return;
 537         }
 538       if (rp)
 539         {
 540           queue_push(solutionq, SOLVER_SOLUTION_BEST);
 541           queue_push(solutionq, rp);
 542         }
 543       return;
 544     }
 545 }
 546
 547 /*
 548  * convert problem data into a form usable for refining.
 549  * Returns the number of problems.
 550  */
 551 int
 552 solver_prepare_solutions(Solver *solv)
 553 {
 554   int i, j = 1, idx;
 555
 556   if (!solv->problems.count)
 557     return 0;
 558   queue_empty(&solv->solutions);
 559   queue_push(&solv->solutions, 0);      /* dummy so idx is always nonzero */
 560   idx = solv->solutions.count;
 561   queue_push(&solv->solutions, -1);     /* unrefined */
 562   /* proofidx stays in position, thus we start with 1 */
 563   for (i = 1; i < solv->problems.count; i++)
 564     {
 565       Id p = solv->problems.elements[i];
 566       queue_push(&solv->solutions, p);
 567       if (p)
 568         continue;
 569       /* end of problem reached */
 570       solv->problems.elements[j++] = idx;
 571       if (i + 1 >= solv->problems.count)
 572         break;
 573       /* start another problem */
 574       solv->problems.elements[j++] = solv->problems.elements[++i];  /* copy proofidx */
 575       idx = solv->solutions.count;
 576       queue_push(&solv->solutions, -1); /* unrefined */
 577     }
 578   solv->problems.count = j;
 579   return j / 2;
 580 }
 581
 582 /*
 583  * refine the simple solution rule list provided by
 584  * the solver into multiple lists of job modifiers.
 585  */
 586 static void
 587 create_solutions(Solver *solv, int probnr, int solidx)
 588 {
 589   Pool *pool = solv->pool;
 590   Queue redoq;
 591   Queue problem, solution, problems_save, branches_save, decisionq_reason_save;
 592   int i, j, nsol;
 593   int essentialok;
 594   unsigned int now;
 595   int oldmistakes = solv->cleandeps_mistakes ? solv->cleandeps_mistakes->count : 0;
 596   Id extraflags = -1;
 597
 598   now = solv_timems(0);
 599   queue_init(&redoq);
 600   /* save decisionq, decisionq_why, decisionmap, and decisioncnt */
 601   for (i = 0; i < solv->decisionq.count; i++)
 602     {
 603       Id p = solv->decisionq.elements[i];
 604       queue_push(&redoq, p);
 605       queue_push(&redoq, solv->decisionq_why.elements[i]);
 606       queue_push(&redoq, solv->decisionmap[p > 0 ? p : -p]);
 607     }
 608
 609   /* save problems queue */
 610   problems_save = solv->problems;
 611   memset(&solv->problems, 0, sizeof(solv->problems));
 612
 613   /* save branches queue */
 614   branches_save = solv->problems;
 615   memset(&solv->branches, 0, sizeof(solv->branches));
 616
 617   /* save decisionq_reason */
 618   decisionq_reason_save = solv->decisionq_reason;
 619   memset(&solv->decisionq_reason, 0, sizeof(solv->decisionq_reason));
 620
 621   /* extract problem from queue */
 622   queue_init(&problem);
 623   for (i = solidx + 1; i < solv->solutions.count; i++)
 624     {
 625       Id v = solv->solutions.elements[i];
 626       if (!v)
 627         break;
 628       queue_push(&problem, v);
 629       if (v < 0)
 630         extraflags &= solv->job.elements[-v - 1];
 631     }
 632   if (extraflags == -1)
 633     extraflags = 0;
 634   if (problem.count > 1)
 635     solv_sort(problem.elements, problem.count, sizeof(Id), problems_sortcmp, &solv->job);
 636   queue_push(&problem, 0);      /* mark end for refine_suggestion */
 637   problem.count--;
 638 #if 0
 639   for (i = 0; i < problem.count; i++)
 640     printf("PP %d %d\n", i, problem.elements[i]);
 641 #endif
 642
 643   /* refine each solution element */
 644   nsol = 0;
 645   essentialok = 0;
 646   queue_init(&solution);
 647   for (i = 0; i < problem.count; i++)
 648     {
 649       int solstart = solv->solutions.count;
 650       refine_suggestion(solv, problem.elements, problem.elements[i], &solution, essentialok);
 651       queue_push(&solv->solutions, 0);  /* reserve room for number of elements */
 652       for (j = 0; j < solution.count; j++)
 653         convertsolution(solv, solution.elements[j], &solv->solutions);
 654       if (solv->solutions.count == solstart + 1)
 655         {
 656           solv->solutions.count--;      /* this one did not work out */
 657           if (nsol || i + 1 < problem.count)
 658             continue;                   /* got one or still hope */
 659           if (!essentialok)
 660             {
 661               /* nothing found, start over */
 662               POOL_DEBUG(SOLV_DEBUG_SOLUTIONS, "nothing found, re-run with essentialok = 1\n");
 663               essentialok = 1;
 664               i = -1;
 665               continue;
 666             }
 667           /* this is bad, we found no solution */
 668           /* for now just offer a rule */
 669           POOL_DEBUG(SOLV_DEBUG_SOLUTIONS, "nothing found, already did essentialok, fake it\n");
 670           queue_push(&solv->solutions, 0);
 671           for (j = 0; j < problem.count; j++)
 672             {
 673               convertsolution(solv, problem.elements[j], &solv->solutions);
 674               if (solv->solutions.count > solstart + 1)
 675                 break;
 676             }
 677           if (solv->solutions.count == solstart + 1)
 678             {
 679               solv->solutions.count--;
 680               continue;         /* sorry */
 681             }
 682         }
 683       /* patch in number of solution elements */
 684       solv->solutions.elements[solstart] = (solv->solutions.count - (solstart + 1)) / 2;
 685       queue_push(&solv->solutions, 0);  /* add end marker */
 686       queue_push(&solv->solutions, 0);  /* add end marker */
 687       queue_push(&solv->solutions, problem.elements[i]);        /* just for bookkeeping */
 688       queue_push(&solv->solutions, extraflags & SOLVER_CLEANDEPS);      /* our extraflags */
 689       solv->solutions.elements[solidx + 1 + nsol++] = solstart;
 690     }
 691   solv->solutions.elements[solidx + 1 + nsol] = 0;      /* end marker */
 692   solv->solutions.elements[solidx] = nsol;
 693   queue_free(&problem);
 694   queue_free(&solution);
 695
 696   /* restore decisions */
 697   memset(solv->decisionmap, 0, pool->nsolvables * sizeof(Id));
 698   queue_empty(&solv->decisionq);
 699   queue_empty(&solv->decisionq_why);
 700   for (i = 0; i < redoq.count; i += 3)
 701     {
 702       Id p = redoq.elements[i];
 703       queue_push(&solv->decisionq, p);
 704       queue_push(&solv->decisionq_why, redoq.elements[i + 1]);
 705       solv->decisionmap[p > 0 ? p : -p] = redoq.elements[i + 2];
 706     }
 707   queue_free(&redoq);
 708
 709   /* restore decision reasons */
 710   queue_free(&solv->decisionq_reason);
 711   solv->decisionq_reason = decisionq_reason_save;
 712
 713   /* restore problems */
 714   queue_free(&solv->problems);
 715   solv->problems = problems_save;
 716
 717   /* restore branches */
 718   queue_free(&solv->branches);
 719   solv->branches = branches_save;
 720
 721   if (solv->cleandeps_mistakes)
 722     {
 723       if (oldmistakes)
 724         queue_truncate(solv->cleandeps_mistakes, oldmistakes);
 725       else
 726         {
 727           queue_free(solv->cleandeps_mistakes);
 728           solv->cleandeps_mistakes = solv_free(solv->cleandeps_mistakes);
 729         }
 730     }
 731
 732   POOL_DEBUG(SOLV_DEBUG_STATS, "create_solutions for problem #%d took %d ms\n", probnr, solv_timems(now));
 733 }
 734
 735
 736 /**************************************************************************/
 737
 738 unsigned int
 739 solver_problem_count(Solver *solv)
 740 {
 741   return solv->problems.count / 2;
 742 }
 743
 744 Id
 745 solver_next_problem(Solver *solv, Id problem)
 746 {
 747   if (!problem)
 748     return solv->problems.count ? 1 : 0;
 749   return (problem + 1) * 2 - 1 < solv->problems.count ? problem + 1 : 0;
 750 }
 751
 752 unsigned int
 753 solver_solution_count(Solver *solv, Id problem)
 754 {
 755   Id solidx = solv->problems.elements[problem * 2 - 1];
 756   if (solv->solutions.elements[solidx] < 0)
 757     create_solutions(solv, problem, solidx);
 758   return solv->solutions.elements[solidx];
 759 }
 760
 761 Id
 762 solver_next_solution(Solver *solv, Id problem, Id solution)
 763 {
 764   Id solidx = solv->problems.elements[problem * 2 - 1];
 765   if (solv->solutions.elements[solidx] < 0)
 766     create_solutions(solv, problem, solidx);
 767   return solv->solutions.elements[solidx + solution + 1] ? solution + 1 : 0;
 768 }
 769
 770 unsigned int
 771 solver_solutionelement_count(Solver *solv, Id problem, Id solution)
 772 {
 773   Id solidx = solv->problems.elements[problem * 2 - 1];
 774   solidx = solv->solutions.elements[solidx + solution];
 775   return solv->solutions.elements[solidx];
 776 }
 777
 778 Id
 779 solver_solutionelement_internalid(Solver *solv, Id problem, Id solution)
 780 {
 781   Id solidx = solv->problems.elements[problem * 2 - 1];
 782   solidx = solv->solutions.elements[solidx + solution];
 783   return solv->solutions.elements[solidx + 2 * solv->solutions.elements[solidx] + 3];
 784 }
 785
 786 Id
 787 solver_solutionelement_extrajobflags(Solver *solv, Id problem, Id solution)
 788 {
 789   Id solidx = solv->problems.elements[problem * 2 - 1];
 790   solidx = solv->solutions.elements[solidx + solution];
 791   return solv->solutions.elements[solidx + 2 * solv->solutions.elements[solidx] + 4];
 792 }
 793
 794
 795 /*
 796  *  return the next item of the proposed solution
 797  *  here are the possibilities for p / rp and what
 798  *  the solver expects the application to do:
 799  *    p                             rp
 800  *  -------------------------------------------------------
 801  *    SOLVER_SOLUTION_INFARCH       pkgid
 802  *    -> add (SOLVER_INSTALL|SOLVER_SOLVABLE, rp) to the job
 803  *    SOLVER_SOLUTION_DISTUPGRADE   pkgid
 804  *    -> add (SOLVER_INSTALL|SOLVER_SOLVABLE, rp) to the job
 805  *    SOLVER_SOLUTION_BEST          pkgid
 806  *    -> add (SOLVER_INSTALL|SOLVER_SOLVABLE, rp) to the job
 807  *    SOLVER_SOLUTION_JOB           jobidx
 808  *    -> remove job (jobidx - 1, jobidx) from job queue
 809  *    SOLVER_SOLUTION_POOLJOB       jobidx
 810  *    -> remove job (jobidx - 1, jobidx) from pool job queue
 811  *    pkgid (> 0)                   0
 812  *    -> add (SOLVER_ERASE|SOLVER_SOLVABLE, p) to the job
 813  *    pkgid (> 0)                   pkgid (> 0)
 814  *    -> add (SOLVER_INSTALL|SOLVER_SOLVABLE, rp) to the job
 815  *       (this will replace package p)
 816  *
 817  * Thus, the solver will either ask the application to remove
 818  * a specific job from the job queue, or ask to add an install/erase
 819  * job to it.
 820  *
 821  */
 822
 823 Id
 824 solver_next_solutionelement(Solver *solv, Id problem, Id solution, Id element, Id *p, Id *rp)
 825 {
 826   Id solidx = solv->problems.elements[problem * 2 - 1];
 827   solidx = solv->solutions.elements[solidx + solution];
 828   if (!solidx)
 829     return 0;
 830   solidx += 1 + element * 2;
 831   if (!solv->solutions.elements[solidx] && !solv->solutions.elements[solidx + 1])
 832     return 0;
 833   *p = solv->solutions.elements[solidx];
 834   *rp = solv->solutions.elements[solidx + 1];
 835   return element + 1;
 836 }
 837
 838 void
 839 solver_take_solutionelement(Solver *solv, Id p, Id rp, Id extrajobflags, Queue *job)
 840 {
 841   int i;
 842
 843   if (p == SOLVER_SOLUTION_POOLJOB)
 844     {
 845       solv->pool->pooljobs.elements[rp - 1] = SOLVER_NOOP;
 846       solv->pool->pooljobs.elements[rp] = 0;
 847       return;
 848     }
 849   if (p == SOLVER_SOLUTION_JOB)
 850     {
 851       job->elements[rp - 1] = SOLVER_NOOP;
 852       job->elements[rp] = 0;
 853       return;
 854     }
 855   if (rp <= 0 && p <= 0)
 856     return;     /* just in case */
 857   if (rp > 0)
 858     p = SOLVER_INSTALL|SOLVER_SOLVABLE|SOLVER_NOTBYUSER|extrajobflags;
 859   else
 860     {
 861       rp = p;
 862       p = SOLVER_ERASE|SOLVER_SOLVABLE|extrajobflags;
 863     }
 864   for (i = 0; i < job->count; i += 2)
 865     if (job->elements[i] == p && job->elements[i + 1] == rp)
 866       return;
 867   queue_push2(job, p, rp);
 868 }
 869
 870 void
 871 solver_take_solution(Solver *solv, Id problem, Id solution, Queue *job)
 872 {
 873   Id p, rp, element = 0;
 874   Id extrajobflags = solver_solutionelement_extrajobflags(solv, problem, solution);
 875   while ((element = solver_next_solutionelement(solv, problem, solution, element, &p, &rp)) != 0)
 876     solver_take_solutionelement(solv, p, rp, extrajobflags, job);
 877 }
 878
 879
 880 /*-------------------------------------------------------------------
 881  *
 882  * find problem rule
 883  */
 884
 885 static void
 886 findproblemrule_internal(Solver *solv, Id idx, Id *reqrp, Id *conrp, Id *sysrp, Id *jobrp, Map *rseen)
 887 {
 888   Id rid, d;
 889   Id lreqr, lconr, lsysr, ljobr;
 890   Rule *r;
 891   Id jobassert = 0;
 892   int i, reqset = 0;    /* 0: unset, 1: installed, 2: jobassert, 3: assert */
 893   int conset = 0;       /* 0: unset, 1: installed */
 894
 895   /* find us a jobassert rule */
 896   for (i = idx; (rid = solv->learnt_pool.elements[i]) != 0; i++)
 897     {
 898       if (rid < solv->jobrules || rid >= solv->jobrules_end)
 899         continue;
 900       r = solv->rules + rid;
 901       d = r->d < 0 ? -r->d - 1 : r->d;
 902       if (!d && r->w2 == 0 && r->p > 0)
 903         {
 904           jobassert = r->p;
 905           break;
 906         }
 907     }
 908
 909   /* the problem rules are somewhat ordered from "near to the problem" to
 910    * "near to the job" */
 911   lreqr = lconr = lsysr = ljobr = 0;
 912   while ((rid = solv->learnt_pool.elements[idx++]) != 0)
 913     {
 914       assert(rid > 0);
 915       if (rid >= solv->learntrules)
 916         {
 917           if (MAPTST(rseen, rid - solv->learntrules))
 918             continue;
 919           MAPSET(rseen, rid - solv->learntrules);
 920           findproblemrule_internal(solv, solv->learnt_why.elements[rid - solv->learntrules], &lreqr, &lconr, &lsysr, &ljobr, rseen);
 921         }
 922       else if ((rid >= solv->jobrules && rid < solv->jobrules_end) || (rid >= solv->infarchrules && rid < solv->infarchrules_end) || (rid >= solv->duprules && rid < solv->duprules_end) || (rid >= solv->bestrules && rid < solv->bestrules_end) || (rid >= solv->yumobsrules && rid <= solv->yumobsrules_end))
 923         {
 924           if (!*jobrp)
 925             *jobrp = rid;
 926         }
 927       else if (rid >= solv->updaterules && rid < solv->updaterules_end)
 928         {
 929           if (!*sysrp)
 930             *sysrp = rid;
 931         }
 932       else
 933         {
 934           assert(rid < solv->pkgrules_end);
 935           r = solv->rules + rid;
 936           d = r->d < 0 ? -r->d - 1 : r->d;
 937           if (!d && r->w2 < 0)
 938             {
 939               /* prefer conflicts of installed packages */
 940               if (solv->installed && !conset)
 941                 {
 942                   if (r->p < 0 && (solv->pool->solvables[-r->p].repo == solv->installed ||
 943                                   solv->pool->solvables[-r->w2].repo == solv->installed))
 944                     {
 945                       *conrp = rid;
 946                       conset = 1;
 947                     }
 948                 }
 949               if (!*conrp)
 950                 *conrp = rid;
 951             }
 952           else
 953             {
 954               if (!d && r->w2 == 0 && reqset < 3)
 955                 {
 956                   if (*reqrp > 0 && r->p < -1)
 957                     {
 958                       Pool *pool = solv->pool;
 959                       Id op = -solv->rules[*reqrp].p;
 960                       if (op > 1 && pool->solvables[op].arch != pool->solvables[-r->p].arch &&
 961                           pool->solvables[op].arch != pool->noarchid &&
 962                           pool->solvables[-r->p].arch != pool->noarchid)
 963                         continue;       /* different arch, skip */
 964                     }
 965                   /* prefer assertions */
 966                   *reqrp = rid;
 967                   reqset = 3;
 968                 }
 969               else if (jobassert && r->p == -jobassert)
 970                 {
 971                   /* prefer rules of job assertions */
 972                   *reqrp = rid;
 973                   reqset = 2;
 974                 }
 975               else if (solv->installed && r->p < 0 && solv->pool->solvables[-r->p].repo == solv->installed && reqset <= 1)
 976                 {
 977                   /* prefer rules of job installed package so that the user doesn't get confused by strange packages */
 978                   *reqrp = rid;
 979                   reqset = 1;
 980                 }
 981               else if (!*reqrp)
 982                 *reqrp = rid;
 983             }
 984         }
 985     }
 986   if (!*reqrp && lreqr)
 987     *reqrp = lreqr;
 988   if (!*conrp && lconr)
 989     *conrp = lconr;
 990   if (!*jobrp && ljobr)
 991     *jobrp = ljobr;
 992   if (!*sysrp && lsysr)
 993     *sysrp = lsysr;
 994 }
 995
 996 /*
 997  * find problem rule
 998  *
 999  * search for a rule that describes the problem to the
1000  * user. Actually a pretty hopeless task that may leave the user
1001  * puzzled. To get all of the needed information use
1002  * solver_findallproblemrules() instead.
1003  */
1004
1005 Id
1006 solver_findproblemrule(Solver *solv, Id problem)
1007 {
1008   Id reqr, conr, sysr, jobr;
1009   Id idx = solv->problems.elements[2 * problem - 2];
1010   Map rseen;
1011   reqr = conr = sysr = jobr = 0;
1012   map_init(&rseen, solv->learntrules ? solv->nrules - solv->learntrules : 0);
1013   findproblemrule_internal(solv, idx, &reqr, &conr, &sysr, &jobr, &rseen);
1014   map_free(&rseen);
1015   /* check if the request is about a not-installed package requiring a installed
1016    * package conflicting with the non-installed package. In that case return the conflict */
1017   if (reqr && conr && solv->installed && solv->rules[reqr].p < 0 && solv->rules[conr].p < 0 && solv->rules[conr].w2 < 0)
1018     {
1019       Pool *pool = solv->pool;
1020       Solvable *s  = pool->solvables - solv->rules[reqr].p;
1021       Solvable *s1 = pool->solvables - solv->rules[conr].p;
1022       Solvable *s2 = pool->solvables - solv->rules[conr].w2;
1023       Id cp = 0;
1024       if (s == s1 && s2->repo == solv->installed)
1025         cp = -solv->rules[conr].w2;
1026       else if (s == s2 && s1->repo == solv->installed)
1027         cp = -solv->rules[conr].p;
1028       if (cp && s1->name != s2->name && s->repo != solv->installed)
1029         {
1030           Id p, pp;
1031           Rule *r = solv->rules + reqr;
1032           FOR_RULELITERALS(p, pp, r)
1033             if (p == cp)
1034               return conr;
1035         }
1036     }
1037   if (reqr)
1038     return reqr;        /* some requires */
1039   if (conr)
1040     return conr;        /* some conflict */
1041   if (sysr)
1042     return sysr;        /* an update rule */
1043   if (jobr)
1044     return jobr;        /* a user request */
1045   assert(0);
1046   return 0;
1047 }
1048
1049 /*-------------------------------------------------------------------*/
1050
1051 static void
1052 findallproblemrules_internal(Solver *solv, Id idx, Queue *rules, Map *rseen)
1053 {
1054   Id rid;
1055   while ((rid = solv->learnt_pool.elements[idx++]) != 0)
1056     {
1057       if (rid >= solv->learntrules)
1058         {
1059           if (MAPTST(rseen, rid - solv->learntrules))
1060             continue;
1061           MAPSET(rseen, rid - solv->learntrules);
1062           findallproblemrules_internal(solv, solv->learnt_why.elements[rid - solv->learntrules], rules, rseen);
1063           continue;
1064         }
1065       queue_pushunique(rules, rid);
1066     }
1067 }
1068
1069 /*
1070  * find all problem rule
1071  *
1072  * return all rules that lead to the problem. This gives the user
1073  * all of the information to understand the problem, but the result
1074  * can be a large number of rules.
1075  */
1076
1077 void
1078 solver_findallproblemrules(Solver *solv, Id problem, Queue *rules)
1079 {
1080   Map rseen;
1081   queue_empty(rules);
1082   map_init(&rseen, solv->learntrules ? solv->nrules - solv->learntrules : 0);
1083   findallproblemrules_internal(solv, solv->problems.elements[2 * problem - 2], rules, &rseen);
1084   map_free(&rseen);
1085 }
1086
1087 const char *
1088 solver_problemruleinfo2str(Solver *solv, SolverRuleinfo type, Id source, Id target, Id dep)
1089 {
1090   Pool *pool = solv->pool;
1091   char *s;
1092   switch (type)
1093     {
1094     case SOLVER_RULE_DISTUPGRADE:
1095       return pool_tmpjoin(pool, pool_solvid2str(pool, source), " does not belong to a distupgrade repository", 0);
1096     case SOLVER_RULE_INFARCH:
1097       return pool_tmpjoin(pool, pool_solvid2str(pool, source), " has inferior architecture", 0);
1098     case SOLVER_RULE_UPDATE:
1099       return pool_tmpjoin(pool, "problem with installed package ", pool_solvid2str(pool, source), 0);
1100     case SOLVER_RULE_JOB:
1101       return "conflicting requests";
1102     case SOLVER_RULE_JOB_UNSUPPORTED:
1103       return "unsupported request";
1104     case SOLVER_RULE_JOB_NOTHING_PROVIDES_DEP:
1105       return pool_tmpjoin(pool, "nothing provides requested ", pool_dep2str(pool, dep), 0);
1106     case SOLVER_RULE_JOB_UNKNOWN_PACKAGE:
1107       return pool_tmpjoin(pool, "package ", pool_dep2str(pool, dep), " does not exist");
1108     case SOLVER_RULE_JOB_PROVIDED_BY_SYSTEM:
1109       return pool_tmpjoin(pool, pool_dep2str(pool, dep), " is provided by the system", 0);
1110     case SOLVER_RULE_PKG:
1111       return "some dependency problem";
1112     case SOLVER_RULE_BEST:
1113       if (source > 0)
1114         return pool_tmpjoin(pool, "cannot install the best update candidate for package ", pool_solvid2str(pool, source), 0);
1115      return "cannot install the best candidate for the job";
1116     case SOLVER_RULE_PKG_NOT_INSTALLABLE:
1117       return pool_tmpjoin(pool, "package ", pool_solvid2str(pool, source), " is not installable");
1118     case SOLVER_RULE_PKG_NOTHING_PROVIDES_DEP:
1119       s = pool_tmpjoin(pool, "nothing provides ", pool_dep2str(pool, dep), 0);
1120       return pool_tmpappend(pool, s, " needed by ", pool_solvid2str(pool, source));
1121     case SOLVER_RULE_PKG_SAME_NAME:
1122       s = pool_tmpjoin(pool, "cannot install both ", pool_solvid2str(pool, source), 0);
1123       return pool_tmpappend(pool, s, " and ", pool_solvid2str(pool, target));
1124     case SOLVER_RULE_PKG_CONFLICTS:
1125       s = pool_tmpjoin(pool, "package ", pool_solvid2str(pool, source), 0);
1126       s = pool_tmpappend(pool, s, " conflicts with ", pool_dep2str(pool, dep));
1127       return pool_tmpappend(pool, s, " provided by ", pool_solvid2str(pool, target));
1128     case SOLVER_RULE_PKG_OBSOLETES:
1129       s = pool_tmpjoin(pool, "package ", pool_solvid2str(pool, source), 0);
1130       s = pool_tmpappend(pool, s, " obsoletes ", pool_dep2str(pool, dep));
1131       return pool_tmpappend(pool, s, " provided by ", pool_solvid2str(pool, target));
1132     case SOLVER_RULE_PKG_INSTALLED_OBSOLETES:
1133       s = pool_tmpjoin(pool, "installed package ", pool_solvid2str(pool, source), 0);
1134       s = pool_tmpappend(pool, s, " obsoletes ", pool_dep2str(pool, dep));
1135       return pool_tmpappend(pool, s, " provided by ", pool_solvid2str(pool, target));
1136     case SOLVER_RULE_PKG_IMPLICIT_OBSOLETES:
1137       s = pool_tmpjoin(pool, "package ", pool_solvid2str(pool, source), 0);
1138       s = pool_tmpappend(pool, s, " implicitly obsoletes ", pool_dep2str(pool, dep));
1139       return pool_tmpappend(pool, s, " provided by ", pool_solvid2str(pool, target));
1140     case SOLVER_RULE_PKG_REQUIRES:
1141       s = pool_tmpjoin(pool, "package ", pool_solvid2str(pool, source), " requires ");
1142       return pool_tmpappend(pool, s, pool_dep2str(pool, dep), ", but none of the providers can be installed");
1143     case SOLVER_RULE_PKG_SELF_CONFLICT:
1144       s = pool_tmpjoin(pool, "package ", pool_solvid2str(pool, source), " conflicts with ");
1145       return pool_tmpappend(pool, s, pool_dep2str(pool, dep), " provided by itself");
1146     case SOLVER_RULE_YUMOBS:
1147       s = pool_tmpjoin(pool, "both package ", pool_solvid2str(pool, source), " and ");
1148       s = pool_tmpjoin(pool, s, pool_solvid2str(pool, target), " obsolete ");
1149       return pool_tmpappend(pool, s, pool_dep2str(pool, dep), 0);
1150     default:
1151       return "bad problem rule type";
1152     }
1153 }
1154
1155 /* convenience function */
1156 const char *
1157 solver_problem2str(Solver *solv, Id problem)
1158 {
1159   Id type, source, target, dep;
1160   Id r = solver_findproblemrule(solv, problem);
1161   if (!r)
1162     return "no problem rule?";
1163   type = solver_ruleinfo(solv, r, &source, &target, &dep);
1164   return solver_problemruleinfo2str(solv, type, source, target, dep);
1165 }
1166
1167 const char *
1168 solver_solutionelement2str(Solver *solv, Id p, Id rp)
1169 {
1170   Pool *pool = solv->pool;
1171   if (p == SOLVER_SOLUTION_JOB || p == SOLVER_SOLUTION_POOLJOB)
1172     {
1173       Id how, what;
1174       if (p == SOLVER_SOLUTION_JOB)
1175         rp += solv->pooljobcnt;
1176       how = solv->job.elements[rp - 1];
1177       what = solv->job.elements[rp];
1178       return pool_tmpjoin(pool, "do not ask to ", pool_job2str(pool, how, what, 0), 0);
1179     }
1180   else if (p == SOLVER_SOLUTION_INFARCH)
1181     {
1182       Solvable *s = pool->solvables + rp;
1183       if (solv->installed && s->repo == solv->installed)
1184         return pool_tmpjoin(pool, "keep ", pool_solvable2str(pool, s), " despite the inferior architecture");
1185       else
1186         return pool_tmpjoin(pool, "install ", pool_solvable2str(pool, s), " despite the inferior architecture");
1187     }
1188   else if (p == SOLVER_SOLUTION_DISTUPGRADE)
1189     {
1190       Solvable *s = pool->solvables + rp;
1191       if (solv->installed && s->repo == solv->installed)
1192         return pool_tmpjoin(pool, "keep obsolete ", pool_solvable2str(pool, s), 0);
1193       else
1194         return pool_tmpjoin(pool, "install ", pool_solvable2str(pool, s), " from excluded repository");
1195     }
1196   else if (p == SOLVER_SOLUTION_BEST)
1197     {
1198       Solvable *s = pool->solvables + rp;
1199       if (solv->installed && s->repo == solv->installed)
1200         return pool_tmpjoin(pool, "keep old ", pool_solvable2str(pool, s), 0);
1201       else
1202         return pool_tmpjoin(pool, "install ", pool_solvable2str(pool, s), " despite the old version");
1203     }
1204   else if (p > 0 && rp == 0)
1205     return pool_tmpjoin(pool, "allow deinstallation of ", pool_solvid2str(pool, p), 0);
1206   else if (p > 0 && rp > 0)
1207     {
1208       const char *sp = pool_solvid2str(pool, p);
1209       const char *srp = pool_solvid2str(pool, rp);
1210       const char *str = pool_tmpjoin(pool, "allow replacement of ", sp, 0);
1211       return pool_tmpappend(pool, str, " with ", srp);
1212     }
1213   else
1214     return "bad solution element";
1215 }
1216