Wind River Support Network

Description

root@qemu0:/# gcc -o hello hello.c
hello.c:7:1: warning: return type defaults to 'int' [-Wimplicit-int]
 main() {
 ^

-----

According to upstream release note on porting to GCC 5.x:
<https://gcc.gnu.org/gcc-5/porting_to.html>

== C language issues ==

* Default standard is now GNU11
GCC defaults to -std=gnu11 instead of -std=gnu89. This brings several changes that users should be aware of. The following paragraphs describe some of these changes and suggest how to deal with them

...

* Some warnings are enabled by default
The C99 mode enables some warnings by default. For instance, GCC warns about missing declarations of functions:

  int
  foo (void)
  {
    return bar ();
  }

This example now gives the following diagnostic:

w.c:4:10: warning: implicit declaration of function 'bar' [-Wimplicit-function-declaration]
   return bar ();
          ^

To suppress this warning add the proper declaration:

  int bar (void);

or use -Wno-implicit-function-declaration.

Another warning that is now turned on by default is the warning about implicit int, as in the following snippet:

  foo (u)
  {
    return u;
  }

This example now gives the following diagnostic:

q.c:1:1: warning: return type defaults to 'int' [-Wimplicit-int]
   foo (u)
   ^
q.c: In function 'foo':
q.c:1:1: warning: type of 'u' defaults to 'int' [-Wimplicit-int]

To suppress this warning just add the proper types:

  int
  foo (int u)
  {
    return u;
  }

or use -Wno-implicit or -Wno-implicit-int.

Another warning that is now turned on by default is the warning about returning no value in a function returning non-void:


  int
  foo (void)
  {
    return;
  }

This example now gives the following diagnostic:

q.c:4:3: warning: 'return' with no value, in function returning non-void
   return;
   ^

The fix is either to specify a proper return value, or to declare the return type of foo as void.

Steps to Reproduce

1)configure --enable-board=qemux86-64 --enable-kernel=standard --enable-rootfs=glibc-std --with-template=feature/target-toolchain

2)make fs

3)make start-target

root@qemu0:/# cat hello.c
#include <stdio.h>

main() {
                printf("Hello World\n");
}

root@qemu0:/# gcc -o hello hello.c
hello.c:7:1: warning: return type defaults to 'int' [-Wimplicit-int]
 main() {
 ^