Bug#276843: gcc-3.4: -O2 disables warning "control reaches end of non-void function"

[Jukka Suomela <debian-reportbug@sammal.pp.fi>]

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.

-- System Information:
Debian Release: 3.1
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 2.6.8-1-686
Locale: LANG=fi_FI, LC_CTYPE=fi_FI

Versions of packages gcc-3.4 depends on:
ii  binutils                    2.15-4       The GNU assembler, linker and bina
ii  cpp-3.4                     3.4.2-2      The GNU C preprocessor
ii  gcc-3.4-base                3.4.2-2      The GNU Compiler Collection (base 
ii  libc6                       2.3.2.ds1-18 GNU C Library: Shared libraries an
ii  libgcc1                     1:3.4.2-2    GCC support library

-- no debconf information