Summary: isolator++ is not compatible with gcc "-static-libstdc++" linker flag.
Steps to reproduce:
- Isolator++ version: 4.1.0
- OS: CentOS or ubuntu
- Install typemock
- add linker flag to makefile at line 168 of \\\"/usr/share/typemock/Examples/Isolator++.Examples.GCC/MakeFile\\\"
ifndef MAKEDEPS
echo Linking $@: $(LD) $(LD_FLAGS) $^ -o $(@) $(LIBS)
$(LD) $(LD_FLAGS) $^ -o $(@) $(LIBS) -pthread -lrt -ldl -Wl,-rpath=$(ISOLATOR_LIBDIR) -static-libstdc++ # new flag here
endi
run `make clean && make `, you will get error 'undefined reference to `std::hash<std::string>::operator()(std::string) const`
Reason:
When you use `std::hash<std::string>::operator()(std::string) const`, it will ends up as an weak but defined symbol in your object file:
$ cat test.cpp
#include <string>
#include <functional>
int main() {
std::string a = "123";
const std::hash<std::string> string_hash{};
std::hash<std::string> const &string_hash_ref = string_hash;
std::size_t str_hash_2 = string_hash_ref(a);
return 0;
}
$ g++ test.cpp -std=c++11
$ readelf -s a.out|c++filt|grep std|grep operator|grep string
72: 0000000000400a18 67 FUNC WEAK DEFAULT 12 std::hash<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::operator()(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const
Unless if it is compiled by some kind of old gcc with std gnu++0x, you may get an undefined symbol in your object file.
Isolator++ seems match in this case:
readelf -s libisolator.a|c++filt|grep std|grep operator|grep string
405: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND std::hash<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::operator()(std::basic_string<char, std::char_traits<char>, std::allocator<char> >) const
420: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND std::hash<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::operator()(std::basic_string<char, std::char_traits<char>, std::allocator<char> >) const
According to the libstdc++ source code, the `std::hash<std::string>::operator()(std::string) const` impl is only supported in the dynamic linked version because of Macro _GLIBCXX_SHARED, see the source code at the reference section.
Reference:
Macro _GLIBCXX_SHARED https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/src/c%2B%2B11/compatibility-c%2B%2B0x.cc#L43
std::hash<std::string>::operator()(std::string) const impl https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/src/c%2B%2B11/compatibility-c%2B%2B0x.cc#L75
