[Bug c/80522] New: Enhancement request: __attribute((warn_untested_result))

["joe at perches dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80522

            Bug ID: 80522
           Summary: Enhancement request:
                    __attribute((warn_untested_result))
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: joe at perches dot com
  Target Milestone: ---

A possibly useful addition similar to:

__attribute__((warn_unused_result))

might be

__attribute__((warn_untested_result))

for things like allocation failures that
are not verified before use.

For instance:

    void *malloc(size_t size);

could become

    void * __attribute((warn_untested_result)) malloc(size_t size)

so that

    #include <stdlib.h>

    struct foo {
            int bar;
    };

    struct foo *alloc_foo(void)
    {
            struct foo *baz = malloc(sizeof(struct foo));
            baz->bar = 1;
            return baz;
    }

The compiler could emit a warning on the set
of baz->bar as an intermediate test of baz
is not performed before any use of baz.

    struct foo *alloc_foo(void)
    {
            struct foo *baz = malloc(sizeof(struct foo));
            if (baz) baz->bar = 1;
            return baz;
    }

This variant would not emit a warning.

Similarly, alloc_foo could use that new attribute.

Martin Sebor also mentioned that non-allocation
functions like fopen could also use this __attribute__
mechanism.