From 70e654ba489ea64e5ba72c63fc56e8a2d5dfd894 Mon Sep 17 00:00:00 2001 From: Ian Lance Taylor Date: Tue, 13 Nov 2007 20:02:32 +0000 Subject: From Craig Silverstein: First cut at detecting ODR violations. --- gold/resolve.cc | 199 ++++++++++++++++++++++++++++++-------------------------- 1 file changed, 105 insertions(+), 94 deletions(-) (limited to 'gold/resolve.cc') diff --git a/gold/resolve.cc b/gold/resolve.cc index 7d141c0..980831b 100644 --- a/gold/resolve.cc +++ b/gold/resolve.cc @@ -119,14 +119,76 @@ static const unsigned int def_flag = 0 << def_undef_or_common_shift; static const unsigned int undef_flag = 1 << def_undef_or_common_shift; static const unsigned int common_flag = 2 << def_undef_or_common_shift; +// This convenience function combines all the flags based on facts +// about the symbol. + +static unsigned int +symbol_to_bits(elfcpp::STB binding, bool is_dynamic, + unsigned int shndx, elfcpp::STT type) +{ + unsigned int bits; + + switch (binding) + { + case elfcpp::STB_GLOBAL: + bits = global_flag; + break; + + case elfcpp::STB_WEAK: + bits = weak_flag; + break; + + case elfcpp::STB_LOCAL: + // We should only see externally visible symbols in the symbol + // table. + gold_error(_("invalid STB_LOCAL symbol in external symbols")); + bits = global_flag; + + default: + // Any target which wants to handle STB_LOOS, etc., needs to + // define a resolve method. + gold_error(_("unsupported symbol binding")); + bits = global_flag; + } + + if (is_dynamic) + bits |= dynamic_flag; + else + bits |= regular_flag; + + switch (shndx) + { + case elfcpp::SHN_UNDEF: + bits |= undef_flag; + break; + + case elfcpp::SHN_COMMON: + bits |= common_flag; + break; + + default: + if (type == elfcpp::STT_COMMON) + bits |= common_flag; + else + bits |= def_flag; + break; + } + + return bits; +} + // Resolve a symbol. This is called the second and subsequent times -// we see a symbol. TO is the pre-existing symbol. SYM is the new -// symbol, seen in OBJECT. VERSION of the version of SYM. +// we see a symbol. TO is the pre-existing symbol. ORIG_SYM is the +// new symbol, seen in OBJECT. SYM is almost always identical to +// ORIG_SYM, but may be munged (for instance, if we determine the +// symbol is in a to-be-discarded section, we'll set sym's shndx to +// UNDEFINED). VERSION of the version of SYM. template void Symbol_table::resolve(Sized_symbol* to, const elfcpp::Sym& sym, + const elfcpp::Sym& orig_sym, Object* object, const char* version) { if (object->target()->has_resolve()) @@ -150,53 +212,10 @@ Symbol_table::resolve(Sized_symbol* to, to->set_in_dyn(); } - unsigned int frombits; - switch (sym.get_st_bind()) - { - case elfcpp::STB_GLOBAL: - frombits = global_flag; - break; - - case elfcpp::STB_WEAK: - frombits = weak_flag; - break; - - case elfcpp::STB_LOCAL: - gold_error(_("%s: invalid STB_LOCAL symbol %s in external symbols"), - object->name().c_str(), to->name()); - frombits = global_flag; - break; - - default: - gold_error(_("%s: unsupported symbol binding %d for symbol %s"), - object->name().c_str(), - static_cast(sym.get_st_bind()), to->name()); - frombits = global_flag; - break; - } - - if (!object->is_dynamic()) - frombits |= regular_flag; - else - frombits |= dynamic_flag; - - switch (sym.get_st_shndx()) - { - case elfcpp::SHN_UNDEF: - frombits |= undef_flag; - break; - - case elfcpp::SHN_COMMON: - frombits |= common_flag; - break; - - default: - if (sym.get_st_type() == elfcpp::STT_COMMON) - frombits |= common_flag; - else - frombits |= def_flag; - break; - } + unsigned int frombits = symbol_to_bits(sym.get_st_bind(), + object->is_dynamic(), + sym.get_st_shndx(), + sym.get_st_type()); bool adjust_common_sizes; if (Symbol_table::should_override(to, frombits, object, @@ -214,6 +233,34 @@ Symbol_table::resolve(Sized_symbol* to, if (adjust_common_sizes && sym.get_st_size() > to->symsize()) to->set_symsize(sym.get_st_size()); } + + // A new weak undefined reference, merging with an old weak + // reference, could be a One Definition Rule (ODR) violation -- + // especially if the types or sizes of the references differ. We'll + // store such pairs and look them up later to make sure they + // actually refer to the same lines of code. (Note: not all ODR + // violations can be found this way, and not everything this finds + // is an ODR violation. But it's helpful to warn about.) + // We use orig_sym here because we want the symbol exactly as it + // appears in the object file, not munged via our future processing. + if (orig_sym.get_st_bind() == elfcpp::STB_WEAK + && to->binding() == elfcpp::STB_WEAK + && orig_sym.get_st_shndx() != elfcpp::SHN_UNDEF + && to->shndx() != elfcpp::SHN_UNDEF + && orig_sym.get_st_size() != 0 // Ignore weird 0-sized symbols. + && to->symsize() != 0 + && (orig_sym.get_st_type() != to->type() + || orig_sym.get_st_size() != to->symsize()) + // C does not have a concept of ODR, so we only need to do this + // on C++ symbols. These have (mangled) names starting with _Z. + && to->name()[0] == '_' && to->name()[1] == 'Z') + { + Symbol_location from_location + = { object, orig_sym.get_st_shndx(), orig_sym.get_st_value() }; + Symbol_location to_location = { to->object(), to->shndx(), to->value() }; + this->candidate_odr_violations_[to->name()].insert(from_location); + this->candidate_odr_violations_[to->name()].insert(to_location); + } } // Handle the core of symbol resolution. This is called with the @@ -229,51 +276,11 @@ Symbol_table::should_override(const Symbol* to, unsigned int frombits, { *adjust_common_sizes = false; - unsigned int tobits; - switch (to->binding()) - { - case elfcpp::STB_GLOBAL: - tobits = global_flag; - break; - - case elfcpp::STB_WEAK: - tobits = weak_flag; - break; - - case elfcpp::STB_LOCAL: - // We should only see externally visible symbols in the symbol - // table. - gold_unreachable(); - - default: - // Any target which wants to handle STB_LOOS, etc., needs to - // define a resolve method. - gold_unreachable(); - } - - if (to->source() == Symbol::FROM_OBJECT - && to->object()->is_dynamic()) - tobits |= dynamic_flag; - else - tobits |= regular_flag; - - switch (to->shndx()) - { - case elfcpp::SHN_UNDEF: - tobits |= undef_flag; - break; - - case elfcpp::SHN_COMMON: - tobits |= common_flag; - break; - - default: - if (to->type() == elfcpp::STT_COMMON) - tobits |= common_flag; - else - tobits |= def_flag; - break; - } + unsigned int tobits = symbol_to_bits(to->binding(), + (to->source() == Symbol::FROM_OBJECT + && to->object()->is_dynamic()), + to->shndx(), + to->type()); // FIXME: Warn if either but not both of TO and SYM are STT_TLS. @@ -719,6 +726,7 @@ void Symbol_table::resolve<32, false>( Sized_symbol<32>* to, const elfcpp::Sym<32, false>& sym, + const elfcpp::Sym<32, false>& orig_sym, Object* object, const char* version); #endif @@ -729,6 +737,7 @@ void Symbol_table::resolve<32, true>( Sized_symbol<32>* to, const elfcpp::Sym<32, true>& sym, + const elfcpp::Sym<32, true>& orig_sym, Object* object, const char* version); #endif @@ -739,6 +748,7 @@ void Symbol_table::resolve<64, false>( Sized_symbol<64>* to, const elfcpp::Sym<64, false>& sym, + const elfcpp::Sym<64, false>& orig_sym, Object* object, const char* version); #endif @@ -749,6 +759,7 @@ void Symbol_table::resolve<64, true>( Sized_symbol<64>* to, const elfcpp::Sym<64, true>& sym, + const elfcpp::Sym<64, true>& orig_sym, Object* object, const char* version); #endif -- cgit v1.1