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 this->object_ = object;
23 this->shnum_ = sym.get_st_shndx(); // FIXME: Handle SHN_XINDEX.
24 this->type_ = sym.get_st_type();
25 this->binding_ = sym.get_st_bind();
26 this->visibility_ = sym.get_st_visibility();
27 this->other_ = sym.get_st_nonvis();
30 // Override the fields in Sized_symbol.
33 template<bool big_endian>
35 Sized_symbol<size>::override(const elfcpp::Sym<size, big_endian>& sym,
38 this->override_base(sym, object);
39 this->value_ = sym.get_st_value();
40 this->size_ = sym.get_st_size();
43 // Resolve a symbol. This is called the second and subsequent times
44 // we see a symbol. TO is the pre-existing symbol. SYM is the new
45 // symbol, seen in OBJECT.
47 template<int size, bool big_endian>
49 Symbol_table::resolve(Sized_symbol<size>* to,
50 const elfcpp::Sym<size, big_endian>& sym,
53 if (object->target()->has_resolve())
55 Sized_target<size, big_endian>* sized_target;
56 #ifdef HAVE_MEMBER_TEMPLATE_SPECIFICATIONS
57 sized_target = object->sized_target<size, big_endian>();
59 Target* target = object->target();
60 assert(target->get_size() == size);
61 assert(target->is_big_endian() ? big_endian : !big_endian);
62 sized_target = static_cast<Sized_target<size, big_endian>*>(target);
64 sized_target->resolve(to, sym, object);
68 // Build a little code for each symbol.
69 // Bit 0: 0 for global, 1 for weak.
70 // Bit 1: 0 for regular object, 1 for shared object
71 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
72 // This gives us values from 0 to 11:
91 switch (to->binding())
93 case elfcpp::STB_GLOBAL:
97 case elfcpp::STB_WEAK:
101 case elfcpp::STB_LOCAL:
102 // We should only see externally visible symbols in the symbol
107 // Any target which wants to handle STB_LOOS, etc., needs to
108 // define a resolve method.
112 if (to->object() != NULL && to->object()->is_dynamic())
117 case elfcpp::SHN_UNDEF:
121 case elfcpp::SHN_COMMON:
126 if (to->type() == elfcpp::STT_COMMON)
132 switch (sym.get_st_bind())
134 case elfcpp::STB_GLOBAL:
138 case elfcpp::STB_WEAK:
142 case elfcpp::STB_LOCAL:
144 _("%s: %s: invalid STB_LOCAL symbol %s in external symbols\n"),
145 program_name, object->name().c_str(), to->name());
150 _("%s: %s: unsupported symbol binding %d for symbol %s\n"),
151 program_name, object->name().c_str(),
152 static_cast<int>(sym.get_st_bind()), to->name());
156 if (object->is_dynamic())
158 frombits |= (1 << 1);
160 // Record that we've seen this symbol in a dynamic object.
164 switch (sym.get_st_shndx())
166 case elfcpp::SHN_UNDEF:
167 frombits |= (1 << 2);
170 case elfcpp::SHN_COMMON:
171 frombits |= (2 << 2);
175 if (sym.get_st_type() == elfcpp::STT_COMMON)
176 frombits |= (2 << 2);
180 // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
182 // We use a giant switch table for symbol resolution. This code is
183 // unwieldy, but: 1) it is efficient; 2) we definitely handle all
184 // cases; 3) it is easy to change the handling of a particular case.
185 // The alternative would be a series of conditionals, but it is easy
186 // to get the ordering wrong. This could also be done as a table,
187 // but that is no easier to understand than this large switch
190 switch (tobits * 16 + frombits)
193 // Two definitions of the same symbol.
194 fprintf(stderr, "%s: %s: multiple definition of %s\n",
195 program_name, object->name().c_str(), to->name());
196 // FIXME: Report locations. Record that we have seen an error.
199 case WEAK_DEF * 16 + DEF:
200 // We've seen a weak definition, and now we see a strong
201 // definition. In the original SVR4 linker, this was treated as
202 // a multiple definition error. In the Solaris linker and the
203 // GNU linker, a weak definition followed by a regular
204 // definition causes the weak definition to be overridden. We
205 // are currently compatible with the GNU linker. In the future
206 // we should add a target specific option to change this.
208 to->override(sym, object);
211 case DYN_DEF * 16 + DEF:
212 case DYN_WEAK_DEF * 16 + DEF:
213 // We've seen a definition in a dynamic object, and now we see a
214 // definition in a regular object. The definition in the
215 // regular object overrides the definition in the dynamic
217 to->override(sym, object);
220 case UNDEF * 16 + DEF:
221 case WEAK_UNDEF * 16 + DEF:
222 case DYN_UNDEF * 16 + DEF:
223 case DYN_WEAK_UNDEF * 16 + DEF:
224 // We've seen an undefined reference, and now we see a
225 // definition. We use the definition.
226 to->override(sym, object);
229 case COMMON * 16 + DEF:
230 case WEAK_COMMON * 16 + DEF:
231 case DYN_COMMON * 16 + DEF:
232 case DYN_WEAK_COMMON * 16 + DEF:
233 // We've seen a common symbol and now we see a definition. The
234 // definition overrides. FIXME: We should optionally issue a
236 to->override(sym, object);
239 case DEF * 16 + WEAK_DEF:
240 case WEAK_DEF * 16 + WEAK_DEF:
241 // We've seen a definition and now we see a weak definition. We
242 // ignore the new weak definition.
245 case DYN_DEF * 16 + WEAK_DEF:
246 case DYN_WEAK_DEF * 16 + WEAK_DEF:
247 // We've seen a dynamic definition and now we see a regular weak
248 // definition. The regular weak definition overrides.
249 to->override(sym, object);
252 case UNDEF * 16 + WEAK_DEF:
253 case WEAK_UNDEF * 16 + WEAK_DEF:
254 case DYN_UNDEF * 16 + WEAK_DEF:
255 case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
256 // A weak definition of a currently undefined symbol.
257 to->override(sym, object);
260 case COMMON * 16 + WEAK_DEF:
261 case WEAK_COMMON * 16 + WEAK_DEF:
262 // A weak definition does not override a common definition.
265 case DYN_COMMON * 16 + WEAK_DEF:
266 case DYN_WEAK_COMMON * 16 + WEAK_DEF:
267 // A weak definition does override a definition in a dynamic
268 // object. FIXME: We should optionally issue a warning.
269 to->override(sym, object);
272 case DEF * 16 + DYN_DEF:
273 case WEAK_DEF * 16 + DYN_DEF:
274 case DYN_DEF * 16 + DYN_DEF:
275 case DYN_WEAK_DEF * 16 + DYN_DEF:
276 // Ignore a dynamic definition if we already have a definition.
279 case UNDEF * 16 + DYN_DEF:
280 case WEAK_UNDEF * 16 + DYN_DEF:
281 case DYN_UNDEF * 16 + DYN_DEF:
282 case DYN_WEAK_UNDEF * 16 + DYN_DEF:
283 // Use a dynamic definition if we have a reference.
284 to->override(sym, object);
287 case COMMON * 16 + DYN_DEF:
288 case WEAK_COMMON * 16 + DYN_DEF:
289 case DYN_COMMON * 16 + DYN_DEF:
290 case DYN_WEAK_COMMON * 16 + DYN_DEF:
291 // Ignore a dynamic definition if we already have a common
295 case DEF * 16 + DYN_WEAK_DEF:
296 case WEAK_DEF * 16 + DYN_WEAK_DEF:
297 case DYN_DEF * 16 + DYN_WEAK_DEF:
298 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
299 // Ignore a weak dynamic definition if we already have a
303 case UNDEF * 16 + DYN_WEAK_DEF:
304 case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
305 case DYN_UNDEF * 16 + DYN_WEAK_DEF:
306 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
307 // Use a weak dynamic definition if we have a reference.
308 to->override(sym, object);
311 case COMMON * 16 + DYN_WEAK_DEF:
312 case WEAK_COMMON * 16 + DYN_WEAK_DEF:
313 case DYN_COMMON * 16 + DYN_WEAK_DEF:
314 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
315 // Ignore a weak dynamic definition if we already have a common
319 case DEF * 16 + UNDEF:
320 case WEAK_DEF * 16 + UNDEF:
321 case DYN_DEF * 16 + UNDEF:
322 case DYN_WEAK_DEF * 16 + UNDEF:
323 case UNDEF * 16 + UNDEF:
324 case WEAK_UNDEF * 16 + UNDEF:
325 case DYN_UNDEF * 16 + UNDEF:
326 case DYN_WEAK_UNDEF * 16 + UNDEF:
327 case COMMON * 16 + UNDEF:
328 case WEAK_COMMON * 16 + UNDEF:
329 case DYN_COMMON * 16 + UNDEF:
330 case DYN_WEAK_COMMON * 16 + UNDEF:
331 // A new undefined reference tells us nothing.
334 case DEF * 16 + WEAK_UNDEF:
335 case WEAK_DEF * 16 + WEAK_UNDEF:
336 case DYN_DEF * 16 + WEAK_UNDEF:
337 case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
338 case UNDEF * 16 + WEAK_UNDEF:
339 case WEAK_UNDEF * 16 + WEAK_UNDEF:
340 case DYN_UNDEF * 16 + WEAK_UNDEF:
341 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
342 case COMMON * 16 + WEAK_UNDEF:
343 case WEAK_COMMON * 16 + WEAK_UNDEF:
344 case DYN_COMMON * 16 + WEAK_UNDEF:
345 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
346 // A new weak undefined reference tells us nothing.
349 case DEF * 16 + DYN_UNDEF:
350 case WEAK_DEF * 16 + DYN_UNDEF:
351 case DYN_DEF * 16 + DYN_UNDEF:
352 case DYN_WEAK_DEF * 16 + DYN_UNDEF:
353 case UNDEF * 16 + DYN_UNDEF:
354 case WEAK_UNDEF * 16 + DYN_UNDEF:
355 case DYN_UNDEF * 16 + DYN_UNDEF:
356 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
357 case COMMON * 16 + DYN_UNDEF:
358 case WEAK_COMMON * 16 + DYN_UNDEF:
359 case DYN_COMMON * 16 + DYN_UNDEF:
360 case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
361 // A new dynamic undefined reference tells us nothing.
364 case DEF * 16 + DYN_WEAK_UNDEF:
365 case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
366 case DYN_DEF * 16 + DYN_WEAK_UNDEF:
367 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
368 case UNDEF * 16 + DYN_WEAK_UNDEF:
369 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
370 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
371 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
372 case COMMON * 16 + DYN_WEAK_UNDEF:
373 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
374 case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
375 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
376 // A new weak dynamic undefined reference tells us nothing.
379 case DEF * 16 + COMMON:
380 // A common symbol does not override a definition.
383 case WEAK_DEF * 16 + COMMON:
384 case DYN_DEF * 16 + COMMON:
385 case DYN_WEAK_DEF * 16 + COMMON:
386 // A common symbol does override a weak definition or a dynamic
388 to->override(sym, object);
391 case UNDEF * 16 + COMMON:
392 case WEAK_UNDEF * 16 + COMMON:
393 case DYN_UNDEF * 16 + COMMON:
394 case DYN_WEAK_UNDEF * 16 + COMMON:
395 // A common symbol is a definition for a reference.
396 to->override(sym, object);
399 case COMMON * 16 + COMMON:
400 case WEAK_COMMON * 16 + COMMON:
401 case DYN_COMMON * 16 + COMMON:
402 case DYN_WEAK_COMMON * 16 + COMMON:
404 case DEF * 16 + WEAK_COMMON:
405 case WEAK_DEF * 16 + WEAK_COMMON:
406 case DYN_DEF * 16 + WEAK_COMMON:
407 case DYN_WEAK_DEF * 16 + WEAK_COMMON:
408 case UNDEF * 16 + WEAK_COMMON:
409 case WEAK_UNDEF * 16 + WEAK_COMMON:
410 case DYN_UNDEF * 16 + WEAK_COMMON:
411 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
412 case COMMON * 16 + WEAK_COMMON:
413 case WEAK_COMMON * 16 + WEAK_COMMON:
414 case DYN_COMMON * 16 + WEAK_COMMON:
415 case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
417 case DEF * 16 + DYN_COMMON:
418 case WEAK_DEF * 16 + DYN_COMMON:
419 case DYN_DEF * 16 + DYN_COMMON:
420 case DYN_WEAK_DEF * 16 + DYN_COMMON:
421 case UNDEF * 16 + DYN_COMMON:
422 case WEAK_UNDEF * 16 + DYN_COMMON:
423 case DYN_UNDEF * 16 + DYN_COMMON:
424 case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
425 case COMMON * 16 + DYN_COMMON:
426 case WEAK_COMMON * 16 + DYN_COMMON:
427 case DYN_COMMON * 16 + DYN_COMMON:
428 case DYN_WEAK_COMMON * 16 + DYN_COMMON:
430 case DEF * 16 + DYN_WEAK_COMMON:
431 case WEAK_DEF * 16 + DYN_WEAK_COMMON:
432 case DYN_DEF * 16 + DYN_WEAK_COMMON:
433 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
434 case UNDEF * 16 + DYN_WEAK_COMMON:
435 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
436 case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
437 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
438 case COMMON * 16 + DYN_WEAK_COMMON:
439 case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
440 case DYN_COMMON * 16 + DYN_WEAK_COMMON:
441 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
450 // Instantiate the templates we need. We could use the configure
451 // script to restrict this to only the ones needed for implemented
456 Symbol_table::resolve<32, true>(
457 Sized_symbol<32>* to,
458 const elfcpp::Sym<32, true>& sym,
463 Symbol_table::resolve<32, false>(
464 Sized_symbol<32>* to,
465 const elfcpp::Sym<32, false>& sym,
470 Symbol_table::resolve<64, true>(
471 Sized_symbol<64>* to,
472 const elfcpp::Sym<64, true>& sym,
477 Symbol_table::resolve<64, false>(
478 Sized_symbol<64>* to,
479 const elfcpp::Sym<64, false>& sym,
482 } // End namespace gold.