Hi guys, I'm trying to get something tricky working, and I think I'm close but I can't seem to get the linker options quite right. I basically have two shared objects that each contain implementations of an allocator type with the same name. What I want is for the code in library A to link against the implementation of the allocator compiled into library A and library B to link against the implementation of the allocator in library B. I started by using -Bsymbolic and -Bsymbolic-functions to try to get each library to use its own internal symbols. The first issue I ran into after that was that by dynamically linking against libstdc++, code in std::basic_streambuf<char, std::char_traits<char> >::xsputn(char const*, long) was dynamically calling libstdc++ which was then calling the wrong implementation of the allocator. After adding the -static-libstdc++ flag at link time, it now bypasses libstdc++ correctly, but manages to directly call the other library's implementation. Here is the offending stack: .../libB.so(+0xad8f9)[0x7f8bdfc758f9] .../libB.so(_ZNSbIcSt11char_traitsIcE18tracking_allocatorIcEE7reserveEm+0x26)[0x7f8bdfc88a16] .../libB.so(_ZNSt15basic_stringbufIcSt11char_traitsIcE18tracking_allocatorIcEE8overflowEi+0x9e)[0x7f8bdfc88b4e] .../libA.so(_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+0x89)[0x7f8bde6a94c9] .../libA.so(_ZSt16__ostream_insertIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_PKS3_l+0x17e)[0x7f8bde69f4be] I dumped the assembly code for the offending function and I get this: Dump of assembler code for function _ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl: 0x00000000002ab440 <+0>: test %rdx,%rdx 0x00000000002ab443 <+3>: push %r14 0x00000000002ab445 <+5>: push %r13 0x00000000002ab447 <+7>: push %r12 0x00000000002ab449 <+9>: push %rbp 0x00000000002ab44a <+10>: push %rbx 0x00000000002ab44b <+11>: jle 0x2ab4e0 <_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+160> 0x00000000002ab451 <+17>: mov %rdi,%r12 0x00000000002ab454 <+20>: mov %rsi,%r14 0x00000000002ab457 <+23>: mov %rdx,%r13 0x00000000002ab45a <+26>: xor %ebx,%ebx 0x00000000002ab45c <+28>: nopl 0x0(%rax) 0x00000000002ab460 <+32>: mov 0x28(%r12),%rdi 0x00000000002ab465 <+37>: mov 0x30(%r12),%rax 0x00000000002ab46a <+42>: sub %rdi,%rax 0x00000000002ab46d <+45>: jne 0x2ab490 <_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+80> 0x00000000002ab46f <+47>: mov (%r12),%rax 0x00000000002ab473 <+51>: mov 0x68(%rax),%rax 0x00000000002ab477 <+55>: cmp 0x2928ea(%rip),%rax # 0x53dd68 0x00000000002ab47e <+62>: jne 0x2ab4c0 <_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+128> 0x00000000002ab480 <+64>: mov %rbx,%rax 0x00000000002ab483 <+67>: pop %rbx 0x00000000002ab484 <+68>: pop %rbp 0x00000000002ab485 <+69>: pop %r12 0x00000000002ab487 <+71>: pop %r13 0x00000000002ab489 <+73>: pop %r14 0x00000000002ab48b <+75>: retq 0x00000000002ab48c <+76>: nopl 0x0(%rax) 0x00000000002ab490 <+80>: mov %r13,%rbp 0x00000000002ab493 <+83>: mov %r14,%rsi 0x00000000002ab496 <+86>: sub %rbx,%rbp 0x00000000002ab499 <+89>: cmp %rax,%rbp 0x00000000002ab49c <+92>: cmovg %rax,%rbp 0x00000000002ab4a0 <+96>: mov %rbp,%rdx 0x00000000002ab4a3 <+99>: add %rbp,%rbx 0x00000000002ab4a6 <+102>: callq 0x98810 <memcpy@plt> 0x00000000002ab4ab <+107>: add %rbp,0x28(%r12) 0x00000000002ab4b0 <+112>: cmp %rbx,%r13 0x00000000002ab4b3 <+115>: jle 0x2ab480 <_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+64> 0x00000000002ab4b5 <+117>: add %rbp,%r14 0x00000000002ab4b8 <+120>: jmp 0x2ab46f <_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+47> 0x00000000002ab4ba <+122>: nopw 0x0(%rax,%rax,1) 0x00000000002ab4c0 <+128>: movzbl (%r14),%esi 0x00000000002ab4c4 <+132>: mov %r12,%rdi 0x00000000002ab4c7 <+135>: callq *%rax 0x00000000002ab4c9 <+137>: cmp $0xffffffffffffffff,%eax 0x00000000002ab4cc <+140>: je 0x2ab480 <_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+64> 0x00000000002ab4ce <+142>: add $0x1,%rbx 0x00000000002ab4d2 <+146>: add $0x1,%r14 0x00000000002ab4d6 <+150>: cmp %rbx,%r13 0x00000000002ab4d9 <+153>: jg 0x2ab460 <_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+32> 0x00000000002ab4db <+155>: jmp 0x2ab480 <_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+64> 0x00000000002ab4dd <+157>: nopl (%rax) 0x00000000002ab4e0 <+160>: xor %ebx,%ebx 0x00000000002ab4e2 <+162>: jmp 0x2ab480 <_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+64> End of assembler dump. The only call I see here that might be related is callq *%rax, but I'm not sure if I'm even doing this right. Both libA and libB have the symbol: _ZNSt15basic_stringbufIcSt11char_traitsIcE18tracking_allocatorIcEE8overflowEi How do I get libA to use its own version of that symbol? I thought that was what -Bsymbolic-functions was supposed to do. Thanks, Nik
