Re: [PATCH 1/2] testsuite: Fix analyzer errors for newlib-errno

[David Malcolm <dmalcolm@redhat.com>]

On Tue, 2023-02-28 at 19:47 +0100, Hans-Peter Nilsson wrote:
> Ok to commit?
> -- >8 --
> Investigating analyzer tesstsuite errors for cris-elf.  The same are
> seen for pru-elf according to posts to gcc-testresults@.
> 
> For glibc, errno is #defined as:
>  extern int *__errno_location (void) __THROW __attribute_const__;
>  # define errno (*__errno_location ())
> while for newlib in its default configuration, it's:
>  #define errno (*__errno())
>  extern int *__errno (void);

We're already handling ___errno (three underscores) for Solaris as of
7c9717fcb5cf94ce1e7ef5c903058adf9980ff28; does it fix the issue if you 
add __errno (two underscores) to analyzer/kf.cc's 
register_known_functions in an analogous way to that commit?  (i.e.
wiring it up to kf_errno_location, "teaching" the analyzer that that
function returns a pointer to the "errno region")

Dave

> 
> The critical difference is that __attribute__ ((__const__)),
> where glibc says that the caller will see the same value on
> all calls (from the same context; read: same thread).  I'm
> not sure the absence of __attribute__ ((__const__)) for the
> newlib definition is deliberate, but I guess it can.
> Either way, without the "const" attribute, it can't be known
> that the same location will be returned the next time, so
> analyzer-tests that depend the value being known it should
> see UNKNOWN rather than TRUE, that's why the deliberate
> check for UNKNOWN rather than xfailing the test.
> 
> For isatty-1.c, it's the same problem, but here it'd be
> unweildy with the extra dg-lines, so better just skip it for
> newlib targets.
> 
> testsuite:
>         * gcc.dg/analyzer/call-summaries-errno.c: Expect UNKNOWN
>         for newlib after having set errno.
>         * gcc.dg/analyzer/errno-1.c: Ditto.
>         * gcc.dg/analyzer/isatty-1.c: Skip for newlib targets.
> ---
>  gcc/testsuite/gcc.dg/analyzer/call-summaries-errno.c | 3 ++-
>  gcc/testsuite/gcc.dg/analyzer/errno-1.c              | 3 ++-
>  gcc/testsuite/gcc.dg/analyzer/isatty-1.c             | 2 +-
>  3 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/gcc/testsuite/gcc.dg/analyzer/call-summaries-errno.c
> b/gcc/testsuite/gcc.dg/analyzer/call-summaries-errno.c
> index e4333b30bb77..cf4d9f7141e4 100644
> --- a/gcc/testsuite/gcc.dg/analyzer/call-summaries-errno.c
> +++ b/gcc/testsuite/gcc.dg/analyzer/call-summaries-errno.c
> @@ -13,5 +13,6 @@ void test_sets_errno (int y)
>    sets_errno (y);
>    sets_errno (y);
>  
> -  __analyzer_eval (errno == y); /* { dg-warning "TRUE" } */  
> +  __analyzer_eval (errno == y); /* { dg-warning "TRUE" "errno is at
> a constant location" { target { ! newlib } } } */
> +  /* { dg-warning "UNKNOWN" "errno is not known to be at a constant
> location" { target { newlib } } .-1 } */
>  }
> diff --git a/gcc/testsuite/gcc.dg/analyzer/errno-1.c
> b/gcc/testsuite/gcc.dg/analyzer/errno-1.c
> index 6b9d28c10799..af0cc3d52a36 100644
> --- a/gcc/testsuite/gcc.dg/analyzer/errno-1.c
> +++ b/gcc/testsuite/gcc.dg/analyzer/errno-1.c
> @@ -17,7 +17,8 @@ void test_storing_to_errno (int val)
>  {
>    __analyzer_eval (errno == val); /* { dg-warning "UNKNOWN" } */
>    errno = val;
> -  __analyzer_eval (errno == val); /* { dg-warning "TRUE" } */
> +  __analyzer_eval (errno == val); /* { dg-warning "TRUE" "errno is
> at a constant location" { target { ! newlib } } } */
> +  /* { dg-warning "UNKNOWN" "errno is not known to be at a constant
> location" { target { newlib } } .-1 } */
>    external_fn ();
>    __analyzer_eval (errno == val); /* { dg-warning "UNKNOWN" } */  
>  }
> diff --git a/gcc/testsuite/gcc.dg/analyzer/isatty-1.c
> b/gcc/testsuite/gcc.dg/analyzer/isatty-1.c
> index 389d2cdf3f18..450a7d71990d 100644
> --- a/gcc/testsuite/gcc.dg/analyzer/isatty-1.c
> +++ b/gcc/testsuite/gcc.dg/analyzer/isatty-1.c
> @@ -1,4 +1,4 @@
> -/* { dg-skip-if "" { powerpc*-*-aix* } } */
> +/* { dg-skip-if "" { powerpc*-*-aix* || newlib } } */
>  
>  #include <errno.h>
>  #include "analyzer-decls.h"