[forwarded from http://bugs.debian.org/276843]
- gcc-3.4.3 -O2 -Wall foo.c doesn't print the warning
foo.c: In function `foo':
foo.c:2: warning: control reaches end of non-void function
gcc-3.3.4 does.
- gcc-4.0 does print a warning, but the warning in 3.3 was
more meaningful for the user:
foo.c: In function 'main':
foo.c:6: warning: '({anonymous})' is used uninitialized in this function
- for the bar.c example, gcc-3.3 and gcc-3.4 don't print any warning,
4.0 prints
foo.c: In function 'main':
foo.c:6: warning: '({anonymous})' is used uninitialized in this function
but probaly could do better.
Matthias
Original report follows:
Package: gcc-3.4
Version: 3.4.2-2
Severity: normal
It seems that if a function in a C program is declared "static", the
type of the function is not void, the programmer forgets to add a
"return" statement, and one compiles the program with gcc using -O2,
gcc gives no warning.
Also it seems that -O3 gives a warning only if there is no return
statement at all. It does not properly detect cases where control can
reach end of function.
Sample session follows.
% cat foo.c
static int foo(void)
{}
int main(void)
{
return foo();
}
% cat bar.c
static int foo(void)
{
if (0) {
return 1;
}
}
int main(void)
{
return foo();
}
% gcc -Wall foo.c
foo.c: In function `foo':
foo.c:2: warning: control reaches end of non-void function
% gcc -Wall -O1 foo.c
foo.c: In function `foo':
foo.c:2: warning: control reaches end of non-void function
% gcc -Wall -O2 foo.c
% gcc -Wall -O3 foo.c
foo.c: In function `foo':
foo.c:2: warning: no return statement in function returning non-void
% gcc -Wall bar.c
bar.c: In function `foo':
bar.c:6: warning: control reaches end of non-void function
% gcc -Wall -O1 bar.c
bar.c: In function `foo':
bar.c:6: warning: control reaches end of non-void function
% gcc -Wall -O2 bar.c
% gcc -Wall -O3 bar.c
% gcc --version
gcc (GCC) 3.4.2 (Debian 3.4.2-2)
Copyright (C) 2004 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.
--
Summary: [3.4 4.0 regression] -O2 disables warning "control
reaches end of non-void function"
Product: gcc
Version: 3.4.3
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: debian-gcc at lists dot debian dot org
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18588
