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 sized_target = object->sized_target SELECT_SIZE_ENDIAN_NAME (
57 SELECT_SIZE_ENDIAN_ONLY(size, big_endian));
58 sized_target->resolve(to, sym, object);
62 // Build a little code for each symbol.
63 // Bit 0: 0 for global, 1 for weak.
64 // Bit 1: 0 for regular object, 1 for shared object
65 // Bits 2-3: 0 for normal, 1 for undefined, 2 for common
66 // This gives us values from 0 to 11:
85 switch (to->binding())
87 case elfcpp::STB_GLOBAL:
91 case elfcpp::STB_WEAK:
95 case elfcpp::STB_LOCAL:
96 // We should only see externally visible symbols in the symbol
101 // Any target which wants to handle STB_LOOS, etc., needs to
102 // define a resolve method.
106 if (to->object() != NULL && to->object()->is_dynamic())
111 case elfcpp::SHN_UNDEF:
115 case elfcpp::SHN_COMMON:
120 if (to->type() == elfcpp::STT_COMMON)
126 switch (sym.get_st_bind())
128 case elfcpp::STB_GLOBAL:
132 case elfcpp::STB_WEAK:
136 case elfcpp::STB_LOCAL:
138 _("%s: %s: invalid STB_LOCAL symbol %s in external symbols\n"),
139 program_name, object->name().c_str(), to->name());
144 _("%s: %s: unsupported symbol binding %d for symbol %s\n"),
145 program_name, object->name().c_str(),
146 static_cast<int>(sym.get_st_bind()), to->name());
150 if (object->is_dynamic())
152 frombits |= (1 << 1);
154 // Record that we've seen this symbol in a dynamic object.
158 switch (sym.get_st_shndx())
160 case elfcpp::SHN_UNDEF:
161 frombits |= (1 << 2);
164 case elfcpp::SHN_COMMON:
165 frombits |= (2 << 2);
169 if (sym.get_st_type() == elfcpp::STT_COMMON)
170 frombits |= (2 << 2);
174 // FIXME: Warn if either but not both of TO and SYM are STT_TLS.
176 // We use a giant switch table for symbol resolution. This code is
177 // unwieldy, but: 1) it is efficient; 2) we definitely handle all
178 // cases; 3) it is easy to change the handling of a particular case.
179 // The alternative would be a series of conditionals, but it is easy
180 // to get the ordering wrong. This could also be done as a table,
181 // but that is no easier to understand than this large switch
184 switch (tobits * 16 + frombits)
187 // Two definitions of the same symbol. We can't give an error
188 // here, because we have not yet discarded linkonce and comdat
192 case WEAK_DEF * 16 + DEF:
193 // We've seen a weak definition, and now we see a strong
194 // definition. In the original SVR4 linker, this was treated as
195 // a multiple definition error. In the Solaris linker and the
196 // GNU linker, a weak definition followed by a regular
197 // definition causes the weak definition to be overridden. We
198 // are currently compatible with the GNU linker. In the future
199 // we should add a target specific option to change this.
201 to->override(sym, object);
204 case DYN_DEF * 16 + DEF:
205 case DYN_WEAK_DEF * 16 + DEF:
206 // We've seen a definition in a dynamic object, and now we see a
207 // definition in a regular object. The definition in the
208 // regular object overrides the definition in the dynamic
210 to->override(sym, object);
213 case UNDEF * 16 + DEF:
214 case WEAK_UNDEF * 16 + DEF:
215 case DYN_UNDEF * 16 + DEF:
216 case DYN_WEAK_UNDEF * 16 + DEF:
217 // We've seen an undefined reference, and now we see a
218 // definition. We use the definition.
219 to->override(sym, object);
222 case COMMON * 16 + DEF:
223 case WEAK_COMMON * 16 + DEF:
224 case DYN_COMMON * 16 + DEF:
225 case DYN_WEAK_COMMON * 16 + DEF:
226 // We've seen a common symbol and now we see a definition. The
227 // definition overrides. FIXME: We should optionally issue a
229 to->override(sym, object);
232 case DEF * 16 + WEAK_DEF:
233 case WEAK_DEF * 16 + WEAK_DEF:
234 // We've seen a definition and now we see a weak definition. We
235 // ignore the new weak definition.
238 case DYN_DEF * 16 + WEAK_DEF:
239 case DYN_WEAK_DEF * 16 + WEAK_DEF:
240 // We've seen a dynamic definition and now we see a regular weak
241 // definition. The regular weak definition overrides.
242 to->override(sym, object);
245 case UNDEF * 16 + WEAK_DEF:
246 case WEAK_UNDEF * 16 + WEAK_DEF:
247 case DYN_UNDEF * 16 + WEAK_DEF:
248 case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
249 // A weak definition of a currently undefined symbol.
250 to->override(sym, object);
253 case COMMON * 16 + WEAK_DEF:
254 case WEAK_COMMON * 16 + WEAK_DEF:
255 // A weak definition does not override a common definition.
258 case DYN_COMMON * 16 + WEAK_DEF:
259 case DYN_WEAK_COMMON * 16 + WEAK_DEF:
260 // A weak definition does override a definition in a dynamic
261 // object. FIXME: We should optionally issue a warning.
262 to->override(sym, object);
265 case DEF * 16 + DYN_DEF:
266 case WEAK_DEF * 16 + DYN_DEF:
267 case DYN_DEF * 16 + DYN_DEF:
268 case DYN_WEAK_DEF * 16 + DYN_DEF:
269 // Ignore a dynamic definition if we already have a definition.
272 case UNDEF * 16 + DYN_DEF:
273 case WEAK_UNDEF * 16 + DYN_DEF:
274 case DYN_UNDEF * 16 + DYN_DEF:
275 case DYN_WEAK_UNDEF * 16 + DYN_DEF:
276 // Use a dynamic definition if we have a reference.
277 to->override(sym, object);
280 case COMMON * 16 + DYN_DEF:
281 case WEAK_COMMON * 16 + DYN_DEF:
282 case DYN_COMMON * 16 + DYN_DEF:
283 case DYN_WEAK_COMMON * 16 + DYN_DEF:
284 // Ignore a dynamic definition if we already have a common
288 case DEF * 16 + DYN_WEAK_DEF:
289 case WEAK_DEF * 16 + DYN_WEAK_DEF:
290 case DYN_DEF * 16 + DYN_WEAK_DEF:
291 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
292 // Ignore a weak dynamic definition if we already have a
296 case UNDEF * 16 + DYN_WEAK_DEF:
297 case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
298 case DYN_UNDEF * 16 + DYN_WEAK_DEF:
299 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
300 // Use a weak dynamic definition if we have a reference.
301 to->override(sym, object);
304 case COMMON * 16 + DYN_WEAK_DEF:
305 case WEAK_COMMON * 16 + DYN_WEAK_DEF:
306 case DYN_COMMON * 16 + DYN_WEAK_DEF:
307 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
308 // Ignore a weak dynamic definition if we already have a common
312 case DEF * 16 + UNDEF:
313 case WEAK_DEF * 16 + UNDEF:
314 case DYN_DEF * 16 + UNDEF:
315 case DYN_WEAK_DEF * 16 + UNDEF:
316 case UNDEF * 16 + UNDEF:
317 case WEAK_UNDEF * 16 + UNDEF:
318 case DYN_UNDEF * 16 + UNDEF:
319 case DYN_WEAK_UNDEF * 16 + UNDEF:
320 case COMMON * 16 + UNDEF:
321 case WEAK_COMMON * 16 + UNDEF:
322 case DYN_COMMON * 16 + UNDEF:
323 case DYN_WEAK_COMMON * 16 + UNDEF:
324 // A new undefined reference tells us nothing.
327 case DEF * 16 + WEAK_UNDEF:
328 case WEAK_DEF * 16 + WEAK_UNDEF:
329 case DYN_DEF * 16 + WEAK_UNDEF:
330 case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
331 case UNDEF * 16 + WEAK_UNDEF:
332 case WEAK_UNDEF * 16 + WEAK_UNDEF:
333 case DYN_UNDEF * 16 + WEAK_UNDEF:
334 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
335 case COMMON * 16 + WEAK_UNDEF:
336 case WEAK_COMMON * 16 + WEAK_UNDEF:
337 case DYN_COMMON * 16 + WEAK_UNDEF:
338 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
339 // A new weak undefined reference tells us nothing.
342 case DEF * 16 + DYN_UNDEF:
343 case WEAK_DEF * 16 + DYN_UNDEF:
344 case DYN_DEF * 16 + DYN_UNDEF:
345 case DYN_WEAK_DEF * 16 + DYN_UNDEF:
346 case UNDEF * 16 + DYN_UNDEF:
347 case WEAK_UNDEF * 16 + DYN_UNDEF:
348 case DYN_UNDEF * 16 + DYN_UNDEF:
349 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
350 case COMMON * 16 + DYN_UNDEF:
351 case WEAK_COMMON * 16 + DYN_UNDEF:
352 case DYN_COMMON * 16 + DYN_UNDEF:
353 case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
354 // A new dynamic undefined reference tells us nothing.
357 case DEF * 16 + DYN_WEAK_UNDEF:
358 case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
359 case DYN_DEF * 16 + DYN_WEAK_UNDEF:
360 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
361 case UNDEF * 16 + DYN_WEAK_UNDEF:
362 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
363 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
364 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
365 case COMMON * 16 + DYN_WEAK_UNDEF:
366 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
367 case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
368 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
369 // A new weak dynamic undefined reference tells us nothing.
372 case DEF * 16 + COMMON:
373 // A common symbol does not override a definition.
376 case WEAK_DEF * 16 + COMMON:
377 case DYN_DEF * 16 + COMMON:
378 case DYN_WEAK_DEF * 16 + COMMON:
379 // A common symbol does override a weak definition or a dynamic
381 to->override(sym, object);
384 case UNDEF * 16 + COMMON:
385 case WEAK_UNDEF * 16 + COMMON:
386 case DYN_UNDEF * 16 + COMMON:
387 case DYN_WEAK_UNDEF * 16 + COMMON:
388 // A common symbol is a definition for a reference.
389 to->override(sym, object);
392 case COMMON * 16 + COMMON:
393 case WEAK_COMMON * 16 + COMMON:
394 case DYN_COMMON * 16 + COMMON:
395 case DYN_WEAK_COMMON * 16 + COMMON:
397 case DEF * 16 + WEAK_COMMON:
398 case WEAK_DEF * 16 + WEAK_COMMON:
399 case DYN_DEF * 16 + WEAK_COMMON:
400 case DYN_WEAK_DEF * 16 + WEAK_COMMON:
401 case UNDEF * 16 + WEAK_COMMON:
402 case WEAK_UNDEF * 16 + WEAK_COMMON:
403 case DYN_UNDEF * 16 + WEAK_COMMON:
404 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
405 case COMMON * 16 + WEAK_COMMON:
406 case WEAK_COMMON * 16 + WEAK_COMMON:
407 case DYN_COMMON * 16 + WEAK_COMMON:
408 case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
410 case DEF * 16 + DYN_COMMON:
411 case WEAK_DEF * 16 + DYN_COMMON:
412 case DYN_DEF * 16 + DYN_COMMON:
413 case DYN_WEAK_DEF * 16 + DYN_COMMON:
414 case UNDEF * 16 + DYN_COMMON:
415 case WEAK_UNDEF * 16 + DYN_COMMON:
416 case DYN_UNDEF * 16 + DYN_COMMON:
417 case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
418 case COMMON * 16 + DYN_COMMON:
419 case WEAK_COMMON * 16 + DYN_COMMON:
420 case DYN_COMMON * 16 + DYN_COMMON:
421 case DYN_WEAK_COMMON * 16 + DYN_COMMON:
423 case DEF * 16 + DYN_WEAK_COMMON:
424 case WEAK_DEF * 16 + DYN_WEAK_COMMON:
425 case DYN_DEF * 16 + DYN_WEAK_COMMON:
426 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
427 case UNDEF * 16 + DYN_WEAK_COMMON:
428 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
429 case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
430 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
431 case COMMON * 16 + DYN_WEAK_COMMON:
432 case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
433 case DYN_COMMON * 16 + DYN_WEAK_COMMON:
434 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
443 // Instantiate the templates we need. We could use the configure
444 // script to restrict this to only the ones needed for implemented
449 Symbol_table::resolve<32, true>(
450 Sized_symbol<32>* to,
451 const elfcpp::Sym<32, true>& sym,
456 Symbol_table::resolve<32, false>(
457 Sized_symbol<32>* to,
458 const elfcpp::Sym<32, false>& sym,
463 Symbol_table::resolve<64, true>(
464 Sized_symbol<64>* to,
465 const elfcpp::Sym<64, true>& sym,
470 Symbol_table::resolve<64, false>(
471 Sized_symbol<64>* to,
472 const elfcpp::Sym<64, false>& sym,
475 } // End namespace gold.