GCC 4.5 -Wall warns if your function has a non-void return type but
returns. It can also detect an infinite loop which means that
"falling off the end" doesn't actually imply a return, and therefore
suppress the warning in that case.
However, if the function is static, this infinite loop detection does
not work:
rich...@deodand:~$ cat t.c
void *a(void) { for(;;); }
static void *b(void) { for(;;) { } }
void foo(void) { b(); }
rich...@deodand:~$ /usr/local/gcc-4.5.0/bin/gcc -c -Wall t.c
t.c: In function b:
t.c:2:1: warning: no return statement in function returning non-void
This real case where I spotted it was a thread function which is
forced to have a return type of 'void *' by the signature of
pthread_create(), but never returns because (by design) the thread
never terminates.
(I assume that the infinite loop detection isn't perfect, but
obviously it shouldn't depend on the linkage of the containing
function.)
rich...@deodand:~$ /usr/local/gcc-4.5.0/bin/gcc --version
gcc (GCC) 4.5.0
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Configured with:
rich...@deodand:~$ ../configure -C --prefix=/usr/local/gcc-4.5.0
--enable-languages=c,c++
rich...@deodand:~$ uname -a
Linux deodand 2.6.32-5-686-bigmem #1 SMP Tue Jun 1 05:38:08 UTC 2010 i686
GNU/Linux
rich...@deodand:~$ dpkg -l libc6
ii libc6 2.11.1-3 Embedded GNU C Library: Shared libraries
--
Summary: Misdetects missing return with non-void return type, but
only if the function is static
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: richard+gcc at sfere dot greenend dot org dot uk
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44511
