http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46713
Summary: -fvisibility=hidden generates broken code
Product: gcc
Version: 4.5.1
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: river+...@tamara.tcx.org.uk
Host: i386-pc-solaris2.10
Target: i386-pc-solaris2.10
Build: i386-pc-solaris2.10
This seems to be identical to a previous problem report on gcc-help[0], which I
ran into recently.
hemlock% gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/opt/ts/lib/gcc/i386-pc-solaris2.10/4.5.1/lto-wrapper
Target: i386-pc-solaris2.10
Configured with: .././configure --prefix=/opt/ts --bindir=/opt/ts/bin
--libdir=/opt/ts/lib --mandir=/opt/ts/share/man --datadir=/opt/ts/share
--includedir=/opt/ts/include --infodir=/opt/ts/share/info
--libexecdir=/opt/ts/lib --sysconfdir=/etc/opt/ts --enable-nls --disable-static
--with-gnu-as --with-as=/opt/ts/binutils/bin/as --with-gnu-ld
--with-ld=/opt/ts/binutils/bin/ld --enable-threads=posix --enable-shared
--enable-multilib --without-x --with-system-zlib
--enable-languages=c,c++,fortran,objc --with-mpfr=/opt/ts --with-gmp=/opt/ts
--with-pkgversion=Toolserver --with-local-prefix=/opt/ts
Thread model: posix
gcc version 4.5.1 (Toolserver)
GNU assembler version 2.20.1 (i386-pc-solaris2.10) using BFD version (GNU
Binutils) 2.20.1.20100303
GNU ld (GNU Binutils) 2.20.1.20100303
also reproducible with: ld: Software Generation Utilities - Solaris Link
Editors: 5.10-1.500
SunOS hemlock 5.10 Generic_142910-17 i86pc i386 i86pc
Test case (test.c):
struct A;
typedef int (*F)(struct A*);
extern const struct A a;
struct A { F f; };
static int f(struct A* x) { return (x==&a); }
const struct A a = { f };
The problem is that when -fvisibility=hidden is used, GCC produces code which
is not accepted by the linker. Removing -fvisibility=hidden fixes the problem.
This is somewhat surprising since GCC claims -fvisibility=hidden is ignored;
so why does it make a difference?
hemlock% gcc -m64 -fPIC -O2 -shared test.c -o test
hemlock% gcc -m64 -fPIC -O2 -shared test.c -o test -fvisibility=hidden
test.c:6:14: warning: visibility attribute not supported in this configuration;
ignored
/opt/ts/binutils/bin/ld: /var/tmp//ccezimpZ.o: relocation R_X86_64_PC32 against
symbol `a' can not be used when making a shared object; recompile with -fPIC
/opt/ts/binutils/bin/ld: final link failed: Bad value
collect2: ld returned 1 exit status
With GNU ld, the tested example works fine in 32-bit mode, but the problem
occurs in 64-bit mode (-m64). With Sun ld, both 32- and 64-bit versions are
broken.
This is a diff of the working asm output, and the broken output (with
-fvisibility) in 64-bit mode:
hemlock% diff -u test.s.working test.s
--- test.s.working 2010-11-29 21:10:20.293575000 +0000
+++ test.s 2010-11-29 21:10:26.449154000 +0000
@@ -4,9 +4,10 @@
.type f, @function
f:
.LFB0:
- xorl %eax, %eax
- cmpq a...@gotpcrel(%rip), %rdi
+ leaq a(%rip), %rax
+ cmpq %rax, %rdi
sete %al
+ movzbl %al, %eax
ret
.LFE0:
.size f, .-f
And the 32-bit diff:
hemlock% diff -u test.s.working test.s
--- test.s.working 2010-11-29 21:14:36.120019000 +0000
+++ test.s 2010-11-29 21:14:37.509620000 +0000
@@ -5,7 +5,7 @@
f:
call .LPR2
addl $_GLOBAL_OFFSET_TABLE_, %ecx
- movl a...@got(%ecx), %eax
+ leal a...@gotoff(%ecx), %eax
cmpl %eax, 4(%esp)
sete %al
movzbl %al, %eax
[0] http://gcc.gnu.org/ml/gcc-help/2008-02/msg00042.html
