1 // resolve.cc -- symbol resolution for gold
13 // Symbol methods used in this file.
15 // Override the fields in Symbol.
17 template<int size, bool big_endian>
19 Symbol::override_base(const elfcpp::Sym<size, big_endian>& sym,
22 assert(this->source_ == FROM_OBJECT);
23 this->u_.from_object.object = object;
24 // FIXME: Handle SHN_XINDEX.
25 this->u_.from_object.shnum = sym.get_st_shndx();
26 this->type_ = sym.get_st_type();
27 this->binding_ = sym.get_st_bind();
28 this->visibility_ = sym.get_st_visibility();
29 this->nonvis_ = sym.get_st_nonvis();
32 // Override the fields in Sized_symbol.
35 template<bool big_endian>
37 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
40 this->override_base(sym, object);
41 this->value_ = sym.get_st_value();
42 this->symsize_ = sym.get_st_size();
45 // Resolve a symbol. This is called the second and subsequent times
46 // we see a symbol. TO is the pre-existing symbol. SYM is the new
47 // symbol, seen in OBJECT.
49 template<int size, bool big_endian>
51 Symbol_table::resolve(Sized_symbol<size>* to,
52 const elfcpp::Sym<size, big_endian>& sym,
55 if (object->target()->has_resolve())
57 Sized_target<size, big_endian>* sized_target;
58 sized_target = object->sized_target SELECT_SIZE_ENDIAN_NAME (
59 SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
60 sized_target->resolve(to, sym, object);
64 // Build a little code for each symbol.
65 // Bit 0: 0 for global, 1 for weak.
66 // Bit 1: 0 for regular object, 1 for shared object
67 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
68 // This gives us values from 0 to 11:
87 switch (to->binding())
89 case elfcpp::STB_GLOBAL:
93 case elfcpp::STB_WEAK:
97 case elfcpp::STB_LOCAL:
98 // We should only see externally visible symbols in the symbol
103 // Any target which wants to handle STB_LOOS, etc., needs to
104 // define a resolve method.
108 if (to->object() != NULL && to->object()->is_dynamic())
113 case elfcpp::SHN_UNDEF:
117 case elfcpp::SHN_COMMON:
122 if (to->type() == elfcpp::STT_COMMON)
128 switch (sym.get_st_bind())
130 case elfcpp::STB_GLOBAL:
134 case elfcpp::STB_WEAK:
138 case elfcpp::STB_LOCAL:
140 _("%s: %s: invalid STB_LOCAL symbol %s in external symbols\n"),
141 program_name, object->name().c_str(), to->name());
146 _("%s: %s: unsupported symbol binding %d for symbol %s\n"),
147 program_name, object->name().c_str(),
148 static_cast<int>(sym.get_st_bind()), to->name());
152 if (object->is_dynamic())
154 frombits |= (1 << 1);
156 // Record that we've seen this symbol in a dynamic object.
160 switch (sym.get_st_shndx())
162 case elfcpp::SHN_UNDEF:
163 frombits |= (1 << 2);
166 case elfcpp::SHN_COMMON:
167 frombits |= (2 << 2);
171 if (sym.get_st_type() == elfcpp::STT_COMMON)
172 frombits |= (2 << 2);
176 // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
178 // We use a giant switch table for symbol resolution. This code is
179 // unwieldy, but: 1) it is efficient; 2) we definitely handle all
180 // cases; 3) it is easy to change the handling of a particular case.
181 // The alternative would be a series of conditionals, but it is easy
182 // to get the ordering wrong. This could also be done as a table,
183 // but that is no easier to understand than this large switch
186 switch (tobits * 16 + frombits)
189 // Two definitions of the same symbol.
190 fprintf(stderr, "%s: %s: multiple definition of %s\n",
191 program_name, object->name().c_str(), to->name());
192 // FIXME: Report locations. Record that we have seen an error.
195 case WEAK_DEF * 16 + DEF:
196 // We've seen a weak definition, and now we see a strong
197 // definition. In the original SVR4 linker, this was treated as
198 // a multiple definition error. In the Solaris linker and the
199 // GNU linker, a weak definition followed by a regular
200 // definition causes the weak definition to be overridden. We
201 // are currently compatible with the GNU linker. In the future
202 // we should add a target specific option to change this.
204 to->override(sym, object);
207 case DYN_DEF * 16 + DEF:
208 case DYN_WEAK_DEF * 16 + DEF:
209 // We've seen a definition in a dynamic object, and now we see a
210 // definition in a regular object. The definition in the
211 // regular object overrides the definition in the dynamic
213 to->override(sym, object);
216 case UNDEF * 16 + DEF:
217 case WEAK_UNDEF * 16 + DEF:
218 case DYN_UNDEF * 16 + DEF:
219 case DYN_WEAK_UNDEF * 16 + DEF:
220 // We've seen an undefined reference, and now we see a
221 // definition. We use the definition.
222 to->override(sym, object);
225 case COMMON * 16 + DEF:
226 case WEAK_COMMON * 16 + DEF:
227 case DYN_COMMON * 16 + DEF:
228 case DYN_WEAK_COMMON * 16 + DEF:
229 // We've seen a common symbol and now we see a definition. The
230 // definition overrides. FIXME: We should optionally issue a
232 to->override(sym, object);
235 case DEF * 16 + WEAK_DEF:
236 case WEAK_DEF * 16 + WEAK_DEF:
237 // We've seen a definition and now we see a weak definition. We
238 // ignore the new weak definition.
241 case DYN_DEF * 16 + WEAK_DEF:
242 case DYN_WEAK_DEF * 16 + WEAK_DEF:
243 // We've seen a dynamic definition and now we see a regular weak
244 // definition. The regular weak definition overrides.
245 to->override(sym, object);
248 case UNDEF * 16 + WEAK_DEF:
249 case WEAK_UNDEF * 16 + WEAK_DEF:
250 case DYN_UNDEF * 16 + WEAK_DEF:
251 case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
252 // A weak definition of a currently undefined symbol.
253 to->override(sym, object);
256 case COMMON * 16 + WEAK_DEF:
257 case WEAK_COMMON * 16 + WEAK_DEF:
258 // A weak definition does not override a common definition.
261 case DYN_COMMON * 16 + WEAK_DEF:
262 case DYN_WEAK_COMMON * 16 + WEAK_DEF:
263 // A weak definition does override a definition in a dynamic
264 // object. FIXME: We should optionally issue a warning.
265 to->override(sym, object);
268 case DEF * 16 + DYN_DEF:
269 case WEAK_DEF * 16 + DYN_DEF:
270 case DYN_DEF * 16 + DYN_DEF:
271 case DYN_WEAK_DEF * 16 + DYN_DEF:
272 // Ignore a dynamic definition if we already have a definition.
275 case UNDEF * 16 + DYN_DEF:
276 case WEAK_UNDEF * 16 + DYN_DEF:
277 case DYN_UNDEF * 16 + DYN_DEF:
278 case DYN_WEAK_UNDEF * 16 + DYN_DEF:
279 // Use a dynamic definition if we have a reference.
280 to->override(sym, object);
283 case COMMON * 16 + DYN_DEF:
284 case WEAK_COMMON * 16 + DYN_DEF:
285 case DYN_COMMON * 16 + DYN_DEF:
286 case DYN_WEAK_COMMON * 16 + DYN_DEF:
287 // Ignore a dynamic definition if we already have a common
291 case DEF * 16 + DYN_WEAK_DEF:
292 case WEAK_DEF * 16 + DYN_WEAK_DEF:
293 case DYN_DEF * 16 + DYN_WEAK_DEF:
294 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
295 // Ignore a weak dynamic definition if we already have a
299 case UNDEF * 16 + DYN_WEAK_DEF:
300 case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
301 case DYN_UNDEF * 16 + DYN_WEAK_DEF:
302 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
303 // Use a weak dynamic definition if we have a reference.
304 to->override(sym, object);
307 case COMMON * 16 + DYN_WEAK_DEF:
308 case WEAK_COMMON * 16 + DYN_WEAK_DEF:
309 case DYN_COMMON * 16 + DYN_WEAK_DEF:
310 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
311 // Ignore a weak dynamic definition if we already have a common
315 case DEF * 16 + UNDEF:
316 case WEAK_DEF * 16 + UNDEF:
317 case DYN_DEF * 16 + UNDEF:
318 case DYN_WEAK_DEF * 16 + UNDEF:
319 case UNDEF * 16 + UNDEF:
320 // A new undefined reference tells us nothing.
323 case WEAK_UNDEF * 16 + UNDEF:
324 case DYN_UNDEF * 16 + UNDEF:
325 case DYN_WEAK_UNDEF * 16 + UNDEF:
326 // A strong undef overrides a dynamic or weak undef.
327 to->override(sym, object);
330 case COMMON * 16 + UNDEF:
331 case WEAK_COMMON * 16 + UNDEF:
332 case DYN_COMMON * 16 + UNDEF:
333 case DYN_WEAK_COMMON * 16 + UNDEF:
334 // A new undefined reference tells us nothing.
337 case DEF * 16 + WEAK_UNDEF:
338 case WEAK_DEF * 16 + WEAK_UNDEF:
339 case DYN_DEF * 16 + WEAK_UNDEF:
340 case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
341 case UNDEF * 16 + WEAK_UNDEF:
342 case WEAK_UNDEF * 16 + WEAK_UNDEF:
343 case DYN_UNDEF * 16 + WEAK_UNDEF:
344 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
345 case COMMON * 16 + WEAK_UNDEF:
346 case WEAK_COMMON * 16 + WEAK_UNDEF:
347 case DYN_COMMON * 16 + WEAK_UNDEF:
348 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
349 // A new weak undefined reference tells us nothing.
352 case DEF * 16 + DYN_UNDEF:
353 case WEAK_DEF * 16 + DYN_UNDEF:
354 case DYN_DEF * 16 + DYN_UNDEF:
355 case DYN_WEAK_DEF * 16 + DYN_UNDEF:
356 case UNDEF * 16 + DYN_UNDEF:
357 case WEAK_UNDEF * 16 + DYN_UNDEF:
358 case DYN_UNDEF * 16 + DYN_UNDEF:
359 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
360 case COMMON * 16 + DYN_UNDEF:
361 case WEAK_COMMON * 16 + DYN_UNDEF:
362 case DYN_COMMON * 16 + DYN_UNDEF:
363 case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
364 // A new dynamic undefined reference tells us nothing.
367 case DEF * 16 + DYN_WEAK_UNDEF:
368 case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
369 case DYN_DEF * 16 + DYN_WEAK_UNDEF:
370 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
371 case UNDEF * 16 + DYN_WEAK_UNDEF:
372 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
373 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
374 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
375 case COMMON * 16 + DYN_WEAK_UNDEF:
376 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
377 case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
378 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
379 // A new weak dynamic undefined reference tells us nothing.
382 case DEF * 16 + COMMON:
383 // A common symbol does not override a definition.
386 case WEAK_DEF * 16 + COMMON:
387 case DYN_DEF * 16 + COMMON:
388 case DYN_WEAK_DEF * 16 + COMMON:
389 // A common symbol does override a weak definition or a dynamic
391 to->override(sym, object);
394 case UNDEF * 16 + COMMON:
395 case WEAK_UNDEF * 16 + COMMON:
396 case DYN_UNDEF * 16 + COMMON:
397 case DYN_WEAK_UNDEF * 16 + COMMON:
398 // A common symbol is a definition for a reference.
399 to->override(sym, object);
402 case COMMON * 16 + COMMON:
403 // Set the size to the maximum.
404 if (sym.get_st_size() > to->symsize())
405 to->set_symsize(sym.get_st_size());
408 case WEAK_COMMON * 16 + COMMON:
409 // I'm not sure just what a weak common symbol means, but
410 // presumably it can be overridden by a regular common symbol.
411 to->override(sym, object);
414 case DYN_COMMON * 16 + COMMON:
415 case DYN_WEAK_COMMON * 16 + COMMON:
417 // Use the real common symbol, but adjust the size if necessary.
418 typename Sized_symbol<size>::Size_type symsize = to->symsize();
419 to->override(sym, object);
420 if (to->symsize() < symsize)
421 to->set_symsize(symsize);
425 case DEF * 16 + WEAK_COMMON:
426 case WEAK_DEF * 16 + WEAK_COMMON:
427 case DYN_DEF * 16 + WEAK_COMMON:
428 case DYN_WEAK_DEF * 16 + WEAK_COMMON:
429 // Whatever a weak common symbol is, it won't override a
433 case UNDEF * 16 + WEAK_COMMON:
434 case WEAK_UNDEF * 16 + WEAK_COMMON:
435 case DYN_UNDEF * 16 + WEAK_COMMON:
436 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
437 // A weak common symbol is better than an undefined symbol.
438 to->override(sym, object);
441 case COMMON * 16 + WEAK_COMMON:
442 case WEAK_COMMON * 16 + WEAK_COMMON:
443 case DYN_COMMON * 16 + WEAK_COMMON:
444 case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
445 // Ignore a weak common symbol in the presence of a real common
449 case DEF * 16 + DYN_COMMON:
450 case WEAK_DEF * 16 + DYN_COMMON:
451 case DYN_DEF * 16 + DYN_COMMON:
452 case DYN_WEAK_DEF * 16 + DYN_COMMON:
453 // Ignore a dynamic common symbol in the presence of a
457 case UNDEF * 16 + DYN_COMMON:
458 case WEAK_UNDEF * 16 + DYN_COMMON:
459 case DYN_UNDEF * 16 + DYN_COMMON:
460 case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
461 // A dynamic common symbol is a definition of sorts.
462 to->override(sym, object);
465 case COMMON * 16 + DYN_COMMON:
466 case WEAK_COMMON * 16 + DYN_COMMON:
467 case DYN_COMMON * 16 + DYN_COMMON:
468 case DYN_WEAK_COMMON * 16 + DYN_COMMON:
469 // Set the size to the maximum.
470 if (sym.get_st_size() > to->symsize())
471 to->set_symsize(sym.get_st_size());
474 case DEF * 16 + DYN_WEAK_COMMON:
475 case WEAK_DEF * 16 + DYN_WEAK_COMMON:
476 case DYN_DEF * 16 + DYN_WEAK_COMMON:
477 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
478 // A common symbol is ignored in the face of a definition.
481 case UNDEF * 16 + DYN_WEAK_COMMON:
482 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
483 case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
484 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
485 // I guess a weak common symbol is better than a definition.
486 to->override(sym, object);
489 case COMMON * 16 + DYN_WEAK_COMMON:
490 case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
491 case DYN_COMMON * 16 + DYN_WEAK_COMMON:
492 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
493 // Set the size to the maximum.
494 if (sym.get_st_size() > to->symsize())
495 to->set_symsize(sym.get_st_size());
503 // Instantiate the templates we need. We could use the configure
504 // script to restrict this to only the ones needed for implemented
509 Symbol_table::resolve<32, true>(
510 Sized_symbol<32>* to,
511 const elfcpp::Sym<32, true>& sym,
516 Symbol_table::resolve<32, false>(
517 Sized_symbol<32>* to,
518 const elfcpp::Sym<32, false>& sym,
523 Symbol_table::resolve<64, true>(
524 Sized_symbol<64>* to,
525 const elfcpp::Sym<64, true>& sym,
530 Symbol_table::resolve<64, false>(
531 Sized_symbol<64>* to,
532 const elfcpp::Sym<64, false>& sym,
535 } // End namespace gold.