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.
188 fprintf(stderr, "%s: %s: multiple definition of %s\n",
189 program_name, object->name().c_str(), to->name());
190 // FIXME: Report locations. Record that we have seen an error.
193 case WEAK_DEF * 16 + DEF:
194 // We've seen a weak definition, and now we see a strong
195 // definition. In the original SVR4 linker, this was treated as
196 // a multiple definition error. In the Solaris linker and the
197 // GNU linker, a weak definition followed by a regular
198 // definition causes the weak definition to be overridden. We
199 // are currently compatible with the GNU linker. In the future
200 // we should add a target specific option to change this.
202 to->override(sym, object);
205 case DYN_DEF * 16 + DEF:
206 case DYN_WEAK_DEF * 16 + DEF:
207 // We've seen a definition in a dynamic object, and now we see a
208 // definition in a regular object. The definition in the
209 // regular object overrides the definition in the dynamic
211 to->override(sym, object);
214 case UNDEF * 16 + DEF:
215 case WEAK_UNDEF * 16 + DEF:
216 case DYN_UNDEF * 16 + DEF:
217 case DYN_WEAK_UNDEF * 16 + DEF:
218 // We've seen an undefined reference, and now we see a
219 // definition. We use the definition.
220 to->override(sym, object);
223 case COMMON * 16 + DEF:
224 case WEAK_COMMON * 16 + DEF:
225 case DYN_COMMON * 16 + DEF:
226 case DYN_WEAK_COMMON * 16 + DEF:
227 // We've seen a common symbol and now we see a definition. The
228 // definition overrides. FIXME: We should optionally issue a
230 to->override(sym, object);
233 case DEF * 16 + WEAK_DEF:
234 case WEAK_DEF * 16 + WEAK_DEF:
235 // We've seen a definition and now we see a weak definition. We
236 // ignore the new weak definition.
239 case DYN_DEF * 16 + WEAK_DEF:
240 case DYN_WEAK_DEF * 16 + WEAK_DEF:
241 // We've seen a dynamic definition and now we see a regular weak
242 // definition. The regular weak definition overrides.
243 to->override(sym, object);
246 case UNDEF * 16 + WEAK_DEF:
247 case WEAK_UNDEF * 16 + WEAK_DEF:
248 case DYN_UNDEF * 16 + WEAK_DEF:
249 case DYN_WEAK_UNDEF * 16 + WEAK_DEF:
250 // A weak definition of a currently undefined symbol.
251 to->override(sym, object);
254 case COMMON * 16 + WEAK_DEF:
255 case WEAK_COMMON * 16 + WEAK_DEF:
256 // A weak definition does not override a common definition.
259 case DYN_COMMON * 16 + WEAK_DEF:
260 case DYN_WEAK_COMMON * 16 + WEAK_DEF:
261 // A weak definition does override a definition in a dynamic
262 // object. FIXME: We should optionally issue a warning.
263 to->override(sym, object);
266 case DEF * 16 + DYN_DEF:
267 case WEAK_DEF * 16 + DYN_DEF:
268 case DYN_DEF * 16 + DYN_DEF:
269 case DYN_WEAK_DEF * 16 + DYN_DEF:
270 // Ignore a dynamic definition if we already have a definition.
273 case UNDEF * 16 + DYN_DEF:
274 case WEAK_UNDEF * 16 + DYN_DEF:
275 case DYN_UNDEF * 16 + DYN_DEF:
276 case DYN_WEAK_UNDEF * 16 + DYN_DEF:
277 // Use a dynamic definition if we have a reference.
278 to->override(sym, object);
281 case COMMON * 16 + DYN_DEF:
282 case WEAK_COMMON * 16 + DYN_DEF:
283 case DYN_COMMON * 16 + DYN_DEF:
284 case DYN_WEAK_COMMON * 16 + DYN_DEF:
285 // Ignore a dynamic definition if we already have a common
289 case DEF * 16 + DYN_WEAK_DEF:
290 case WEAK_DEF * 16 + DYN_WEAK_DEF:
291 case DYN_DEF * 16 + DYN_WEAK_DEF:
292 case DYN_WEAK_DEF * 16 + DYN_WEAK_DEF:
293 // Ignore a weak dynamic definition if we already have a
297 case UNDEF * 16 + DYN_WEAK_DEF:
298 case WEAK_UNDEF * 16 + DYN_WEAK_DEF:
299 case DYN_UNDEF * 16 + DYN_WEAK_DEF:
300 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_DEF:
301 // Use a weak dynamic definition if we have a reference.
302 to->override(sym, object);
305 case COMMON * 16 + DYN_WEAK_DEF:
306 case WEAK_COMMON * 16 + DYN_WEAK_DEF:
307 case DYN_COMMON * 16 + DYN_WEAK_DEF:
308 case DYN_WEAK_COMMON * 16 + DYN_WEAK_DEF:
309 // Ignore a weak dynamic definition if we already have a common
313 case DEF * 16 + UNDEF:
314 case WEAK_DEF * 16 + UNDEF:
315 case DYN_DEF * 16 + UNDEF:
316 case DYN_WEAK_DEF * 16 + UNDEF:
317 case UNDEF * 16 + UNDEF:
318 case WEAK_UNDEF * 16 + UNDEF:
319 case DYN_UNDEF * 16 + UNDEF:
320 case DYN_WEAK_UNDEF * 16 + UNDEF:
321 case COMMON * 16 + UNDEF:
322 case WEAK_COMMON * 16 + UNDEF:
323 case DYN_COMMON * 16 + UNDEF:
324 case DYN_WEAK_COMMON * 16 + UNDEF:
325 // A new undefined reference tells us nothing.
328 case DEF * 16 + WEAK_UNDEF:
329 case WEAK_DEF * 16 + WEAK_UNDEF:
330 case DYN_DEF * 16 + WEAK_UNDEF:
331 case DYN_WEAK_DEF * 16 + WEAK_UNDEF:
332 case UNDEF * 16 + WEAK_UNDEF:
333 case WEAK_UNDEF * 16 + WEAK_UNDEF:
334 case DYN_UNDEF * 16 + WEAK_UNDEF:
335 case DYN_WEAK_UNDEF * 16 + WEAK_UNDEF:
336 case COMMON * 16 + WEAK_UNDEF:
337 case WEAK_COMMON * 16 + WEAK_UNDEF:
338 case DYN_COMMON * 16 + WEAK_UNDEF:
339 case DYN_WEAK_COMMON * 16 + WEAK_UNDEF:
340 // A new weak undefined reference tells us nothing.
343 case DEF * 16 + DYN_UNDEF:
344 case WEAK_DEF * 16 + DYN_UNDEF:
345 case DYN_DEF * 16 + DYN_UNDEF:
346 case DYN_WEAK_DEF * 16 + DYN_UNDEF:
347 case UNDEF * 16 + DYN_UNDEF:
348 case WEAK_UNDEF * 16 + DYN_UNDEF:
349 case DYN_UNDEF * 16 + DYN_UNDEF:
350 case DYN_WEAK_UNDEF * 16 + DYN_UNDEF:
351 case COMMON * 16 + DYN_UNDEF:
352 case WEAK_COMMON * 16 + DYN_UNDEF:
353 case DYN_COMMON * 16 + DYN_UNDEF:
354 case DYN_WEAK_COMMON * 16 + DYN_UNDEF:
355 // A new dynamic undefined reference tells us nothing.
358 case DEF * 16 + DYN_WEAK_UNDEF:
359 case WEAK_DEF * 16 + DYN_WEAK_UNDEF:
360 case DYN_DEF * 16 + DYN_WEAK_UNDEF:
361 case DYN_WEAK_DEF * 16 + DYN_WEAK_UNDEF:
362 case UNDEF * 16 + DYN_WEAK_UNDEF:
363 case WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
364 case DYN_UNDEF * 16 + DYN_WEAK_UNDEF:
365 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_UNDEF:
366 case COMMON * 16 + DYN_WEAK_UNDEF:
367 case WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
368 case DYN_COMMON * 16 + DYN_WEAK_UNDEF:
369 case DYN_WEAK_COMMON * 16 + DYN_WEAK_UNDEF:
370 // A new weak dynamic undefined reference tells us nothing.
373 case DEF * 16 + COMMON:
374 // A common symbol does not override a definition.
377 case WEAK_DEF * 16 + COMMON:
378 case DYN_DEF * 16 + COMMON:
379 case DYN_WEAK_DEF * 16 + COMMON:
380 // A common symbol does override a weak definition or a dynamic
382 to->override(sym, object);
385 case UNDEF * 16 + COMMON:
386 case WEAK_UNDEF * 16 + COMMON:
387 case DYN_UNDEF * 16 + COMMON:
388 case DYN_WEAK_UNDEF * 16 + COMMON:
389 // A common symbol is a definition for a reference.
390 to->override(sym, object);
393 case COMMON * 16 + COMMON:
394 case WEAK_COMMON * 16 + COMMON:
395 case DYN_COMMON * 16 + COMMON:
396 case DYN_WEAK_COMMON * 16 + COMMON:
398 case DEF * 16 + WEAK_COMMON:
399 case WEAK_DEF * 16 + WEAK_COMMON:
400 case DYN_DEF * 16 + WEAK_COMMON:
401 case DYN_WEAK_DEF * 16 + WEAK_COMMON:
402 case UNDEF * 16 + WEAK_COMMON:
403 case WEAK_UNDEF * 16 + WEAK_COMMON:
404 case DYN_UNDEF * 16 + WEAK_COMMON:
405 case DYN_WEAK_UNDEF * 16 + WEAK_COMMON:
406 case COMMON * 16 + WEAK_COMMON:
407 case WEAK_COMMON * 16 + WEAK_COMMON:
408 case DYN_COMMON * 16 + WEAK_COMMON:
409 case DYN_WEAK_COMMON * 16 + WEAK_COMMON:
411 case DEF * 16 + DYN_COMMON:
412 case WEAK_DEF * 16 + DYN_COMMON:
413 case DYN_DEF * 16 + DYN_COMMON:
414 case DYN_WEAK_DEF * 16 + DYN_COMMON:
415 case UNDEF * 16 + DYN_COMMON:
416 case WEAK_UNDEF * 16 + DYN_COMMON:
417 case DYN_UNDEF * 16 + DYN_COMMON:
418 case DYN_WEAK_UNDEF * 16 + DYN_COMMON:
419 case COMMON * 16 + DYN_COMMON:
420 case WEAK_COMMON * 16 + DYN_COMMON:
421 case DYN_COMMON * 16 + DYN_COMMON:
422 case DYN_WEAK_COMMON * 16 + DYN_COMMON:
424 case DEF * 16 + DYN_WEAK_COMMON:
425 case WEAK_DEF * 16 + DYN_WEAK_COMMON:
426 case DYN_DEF * 16 + DYN_WEAK_COMMON:
427 case DYN_WEAK_DEF * 16 + DYN_WEAK_COMMON:
428 case UNDEF * 16 + DYN_WEAK_COMMON:
429 case WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
430 case DYN_UNDEF * 16 + DYN_WEAK_COMMON:
431 case DYN_WEAK_UNDEF * 16 + DYN_WEAK_COMMON:
432 case COMMON * 16 + DYN_WEAK_COMMON:
433 case WEAK_COMMON * 16 + DYN_WEAK_COMMON:
434 case DYN_COMMON * 16 + DYN_WEAK_COMMON:
435 case DYN_WEAK_COMMON * 16 + DYN_WEAK_COMMON:
444 // Instantiate the templates we need. We could use the configure
445 // script to restrict this to only the ones needed for implemented
450 Symbol_table::resolve<32, true>(
451 Sized_symbol<32>* to,
452 const elfcpp::Sym<32, true>& sym,
457 Symbol_table::resolve<32, false>(
458 Sized_symbol<32>* to,
459 const elfcpp::Sym<32, false>& sym,
464 Symbol_table::resolve<64, true>(
465 Sized_symbol<64>* to,
466 const elfcpp::Sym<64, true>& sym,
471 Symbol_table::resolve<64, false>(
472 Sized_symbol<64>* to,
473 const elfcpp::Sym<64, false>& sym,
476 } // End namespace gold.