Bug#536570: gcc-4.3: Redeclaration with different visibility isn't spotted when using -fvisibility=hidden

[Mike Hommey <mh+reportbug@glandium.org>]

Package: gcc-4.3
Version: 4.3.3-13
Severity: normal

When using -fvisibility=hidden to define the global visibility to hidden,
declaring a function with the global visibility, then redeclaring it
with visibility default results in the symbol being exported.

$ cat > test.c <<EOF
extern int foo();

__attribute__((visibility("default"))) int foo() {
   return 42;
}
EOF
$ gcc -fvisibility=hidden -o test.o -c test.c
$ objdump -x test.o | grep foo
0000000000000000 g     F .text	000000000000000b foo

When using #pragma GCC visibility push(hidden) to define the global
visibility to hidden, declaring a function with the global visibilty,
then redeclaring it with visibility default results in a warning about
this redeclaration, and the symbol being hidden.

$ cat > test.c <<EOF
#pragma GCC visibility push(hidden)

extern int foo();

__attribute__((visibility("default"))) int foo() {
   return 42;
}
$ gcc -o test.o -c test.c
test.c:5: warning: redeclaration of ‘foo’ with different visibility (old visibility preserved)
test.c:3: warning: previous declaration of ‘foo’ was here
$ objdump -x test.o | grep foo
0000000000000000 g     F .text	000000000000000b .hidden foo

I think the latter is better, and the inconsistency is harmful.

Mike

-- System Information:
Debian Release: squeeze/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.30-1-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages gcc-4.3 depends on:
ii  binutils              2.19.51.20090704-1 The GNU assembler, linker and bina
ii  cpp-4.3               4.3.3-13           The GNU C preprocessor
ii  gcc-4.3-base          4.3.3-13           The GNU Compiler Collection (base 
ii  libc6                 2.9-13             GNU C Library: Shared libraries
ii  libgcc1               1:4.4.0-7          GCC support library

Versions of packages gcc-4.3 recommends:
ii  libc6-dev                     2.9-13     GNU C Library: Development Librari

Versions of packages gcc-4.3 suggests:
pn  gcc-4.3-doc                   <none>     (no description available)
pn  gcc-4.3-locales               <none>     (no description available)
pn  gcc-4.3-multilib              <none>     (no description available)
pn  libgcc1-dbg                   <none>     (no description available)
pn  libgomp1-dbg                  <none>     (no description available)
pn  libmudflap0-4.3-dev           <none>     (no description available)
pn  libmudflap0-dbg               <none>     (no description available)

-- no debconf information