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-fvisibility-inlines-hidden not hiding inline methods?

From: Lassi Tuura <lat at cern dot ch>
To: <gcc-help at gcc dot gnu dot org>
Cc: Peter Elmer <Peter dot Elmer at cern dot ch>, Giulio Eulisse <Giulio dot Eulisse at cern dot ch>
Date: Fri, 10 Jul 2009 16:00:36 +0200
Subject: -fvisibility-inlines-hidden not hiding inline methods?

Hi,

We are using GCC 4.3.2 + binutils 2.19.1 on a RHEL4-derived system. We're testing -fvisibility-inlines-hidden, and don't quite understand what it does. We are seeing some but not all inline functions getting emitted out-of-line as public weak symbols and calls to them going via the PLT; the documentation seems to indicate this would not happen.

I've stared at this for a while and fail to see the logic by which something is emitted as hidden or as a (weak) default visibility symbols. We use several libraries beyond the standard library, and in any shared library we may have 2/3rds declared default and 1/3rd declared hidden for example (e.g. for boost).

I've made below a very simple example using a std::vector and std::sort. As you can see from the readelf and objdump outputs attached below, calls to local inlined functions have default visibility and go via PLT, so it seems -fvisibility-inlines-hidden didn't really achieve its purpose here.

Have we misunderstood the intended behaviour or is there a bug or incompatibility here somewhere?

Regards,
Lassi


$ cat foo.cc
#include <vector>
#include <algorithm>

int foo(int *a, int *b)
{
  std::vector<int> x(a, b);
  std::sort(x.begin(), x.end());
  return x[0];
}

$ c++ -v Using built-in specs. Target: x86_64-unknown-linux-gnu Configured with: ../configure --prefix=/build/31c/slc4_amd64_gcc432/ external/gcc/4.3.2 --enable-languages=c,c++,fortran --with-gmp=/build/ 31c/slc4_amd64_gcc432/external/gcc/4.3.2/tmp/gmp --with-mpfr=/build/ 31c/slc4_amd64_gcc432/external/gcc/4.3.2/tmp/mpfr --enable-shared Thread model: posix gcc version 4.3.2 (GCC)

$ as --version GNU assembler (GNU Binutils) 2.19.1 Copyright 2007 Free Software Foundation, Inc. This program is free software; you may redistribute it under the terms of the GNU General Public License version 3 or later. This program has absolutely no warranty. This assembler was configured for a target of `x86_64-unknown-linux- gnu'.

$ ld --version GNU ld (GNU Binutils) 2.19.1 Copyright 2007 Free Software Foundation, Inc. This program is free software; you may redistribute it under the terms of the GNU General Public License version 3 or (at your option) a later version. This program has absolutely no warranty.

$ c++ -shared -o libfoo.so -fPIC -fvisibility-inlines-hidden -O2 -W - Wall foo.cc

$ readelf -Ws libfoo.so | awk '/dynsym/,/^$/ {print}{}' Symbol table '.dynsym' contains 20 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 00000000000007a0 0 SECTION LOCAL DEFAULT 8 2: 0000000000000a80 242 FUNC WEAK DEFAULT 10 _ZSt13__adjust_heapIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEEE liEvT_T0_S8_T1_ 3: 0000000000000940 314 FUNC GLOBAL DEFAULT 10 _Z3fooPiS_ 4: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__ 5: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _Jv_RegisterClasses 6: 0000000000000000 0 FUNC GLOBAL DEFAULT UND _ZdlPv@GLIBCXX_3.4 (2) 7: 0000000000000dc8 0 FUNC GLOBAL DEFAULT 11 _fini 8: 0000000000000b80 365 FUNC WEAK DEFAULT 10 _ZSt16__introsort_loopIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiE EEElEvT_S7_T0_ 9: 0000000000000000 0 FUNC WEAK DEFAULT UND __cxa_finalize@GLIBC_2.2.5 (3) 10: 0000000000000000 0 FUNC GLOBAL DEFAULT UND memmove@GLIBC_2.2.5 (3) 11: 0000000000001260 0 NOTYPE GLOBAL DEFAULT ABS __bss_start 12: 0000000000001270 0 NOTYPE GLOBAL DEFAULT ABS _end 13: 0000000000000cf0 155 FUNC WEAK DEFAULT 10 _ZSt16__insertion_sortIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiE EEEEvT_S7_ 14: 0000000000000000 0 FUNC GLOBAL DEFAULT UND _ZSt17__throw_bad_allocv@GLIBCXX_3.4 (2) 15: 0000000000001260 0 NOTYPE GLOBAL DEFAULT ABS _edata 16: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __gxx_personality_v0@CXXABI_1.3 (4) 17: 0000000000000000 0 FUNC GLOBAL DEFAULT UND _Znwm@GLIBCXX_3.4 (2) 18: 0000000000000000 0 FUNC GLOBAL DEFAULT UND _Unwind_Resume@GCC_3.0 (5) 19: 00000000000007a0 0 FUNC GLOBAL DEFAULT 8 _init

$ objdump -j .plt -d libfoo.so

libfoo.so: file format elf64-x86-64

Disassembly of section .plt:

00000000000007b8 <_ZSt13__adjust_heapIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEE EliEvT_T0_S8_T1_@plt-0x10>: 7b8: ff 35 3a 0a 00 00 pushq 0xa3a(%rip) # 11f8 <_GLOBAL_OFFSET_TABLE_+0x8> 7be: ff 25 3c 0a 00 00 jmpq *0xa3c(%rip) # 1200 <_GLOBAL_OFFSET_TABLE_+0x10> 7c4: 0f 1f 40 00 nopl 0x0(%rax)

00000000000007c8 <_ZSt13__adjust_heapIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEE EliEvT_T0_S8_T1_@plt>: 7c8: ff 25 3a 0a 00 00 jmpq *0xa3a(%rip) # 1208 <_GLOBAL_OFFSET_TABLE_+0x18> 7ce: 68 00 00 00 00 pushq $0x0 7d3: e9 e0 ff ff ff jmpq 7b8 <_init+0x18>

00000000000007d8 <_ZdlPv@plt>: 7d8: ff 25 32 0a 00 00 jmpq *0xa32(%rip) # 1210 <_GLOBAL_OFFSET_TABLE_+0x20> 7de: 68 01 00 00 00 pushq $0x1 7e3: e9 d0 ff ff ff jmpq 7b8 <_init+0x18>

00000000000007e8 <_ZSt16__introsort_loopIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIi EEEElEvT_S7_T0_@plt>: 7e8: ff 25 2a 0a 00 00 jmpq *0xa2a(%rip) # 1218 <_GLOBAL_OFFSET_TABLE_+0x28> 7ee: 68 02 00 00 00 pushq $0x2 7f3: e9 c0 ff ff ff jmpq 7b8 <_init+0x18>

00000000000007f8 <__cxa_finalize@plt>: 7f8: ff 25 22 0a 00 00 jmpq *0xa22(%rip) # 1220 <_GLOBAL_OFFSET_TABLE_+0x30> 7fe: 68 03 00 00 00 pushq $0x3 803: e9 b0 ff ff ff jmpq 7b8 <_init+0x18>

0000000000000808 <memmove@plt>: 808: ff 25 1a 0a 00 00 jmpq *0xa1a(%rip) # 1228 <_GLOBAL_OFFSET_TABLE_+0x38> 80e: 68 04 00 00 00 pushq $0x4 813: e9 a0 ff ff ff jmpq 7b8 <_init+0x18>

0000000000000818 <_ZSt16__insertion_sortIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIi EEEEEvT_S7_@plt>: 818: ff 25 12 0a 00 00 jmpq *0xa12(%rip) # 1230 <_GLOBAL_OFFSET_TABLE_+0x40> 81e: 68 05 00 00 00 pushq $0x5 823: e9 90 ff ff ff jmpq 7b8 <_init+0x18>

0000000000000828 <_ZSt17__throw_bad_allocv@plt>: 828: ff 25 0a 0a 00 00 jmpq *0xa0a(%rip) # 1238 <_GLOBAL_OFFSET_TABLE_+0x48> 82e: 68 06 00 00 00 pushq $0x6 833: e9 80 ff ff ff jmpq 7b8 <_init+0x18>

0000000000000838 <_Znwm@plt>: 838: ff 25 02 0a 00 00 jmpq *0xa02(%rip) # 1240 <_GLOBAL_OFFSET_TABLE_+0x50> 83e: 68 07 00 00 00 pushq $0x7 843: e9 70 ff ff ff jmpq 7b8 <_init+0x18>

0000000000000848 <_Unwind_Resume@plt>: 848: ff 25 fa 09 00 00 jmpq *0x9fa(%rip) # 1248 <_GLOBAL_OFFSET_TABLE_+0x58> 84e: 68 08 00 00 00 pushq $0x8 853: e9 60 ff ff ff jmpq 7b8 <_init+0x18>

$ objdump -j .text -d libfoo.so | grep "callq.*@plt" 8a1: e8 52 ff ff ff callq 7f8 <__cxa_finalize@plt> 975: e8 be fe ff ff callq 838 <_Znwm@plt> 98b: e8 78 fe ff ff callq 808 <memmove@plt> 9c0: e8 23 fe ff ff callq 7e8 <_ZSt16__introsort_loopIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIi EEEElEvT_S7_T0_@plt> 9d5: e8 3e fe ff ff callq 818 <_ZSt16__insertion_sortIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIi EEEEEvT_S7_@plt> a29: e8 aa fd ff ff callq 7d8 <_ZdlPv@plt> a3b: e8 d8 fd ff ff callq 818 <_ZSt16__insertion_sortIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIi EEEEEvT_S7_@plt> a50: e8 d3 fd ff ff callq 828 <_ZSt17__throw_bad_allocv@plt> a65: e8 6e fd ff ff callq 7d8 <_ZdlPv@plt> a6d: e8 d6 fd ff ff callq 848 <_Unwind_Resume@plt> a75: e8 ce fd ff ff callq 848 <_Unwind_Resume@plt> c34: e8 af fb ff ff callq 7e8 <_ZSt16__introsort_loopIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIi EEEElEvT_S7_T0_@plt> c7e: e8 45 fb ff ff callq 7c8 <_ZSt13__adjust_heapIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEE EliEvT_T0_S8_T1_@plt> cb3: e8 10 fb ff ff callq 7c8 <_ZSt13__adjust_heapIN9__gnu_cxx17__normal_iteratorIPiSt6vectorIiSaIiEEE EliEvT_T0_S8_T1_@plt> d6d: e8 96 fa ff ff callq 808 <memmove@plt>

Follow-Ups:
- Re: -fvisibility-inlines-hidden not hiding inline methods?
  - From: Ian Lance Taylor

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