Re: [PATCH] gimple-fold: fix further missing stmt locations [PR104308]

[Richard Biener <richard.guenther@gmail.com>]

On Thu, Apr 14, 2022 at 3:25 PM David Malcolm via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> PR analyzer/104308 initially reported about a
> -Wanalyzer-use-of-uninitialized-value diagnostic using UNKNOWN_LOCATION
> when complaining about certain memmove operations where the source
> is uninitialized.
>
> In r12-7856-g875342766d4298 I fixed the missing location for
> a stmt generated by gimple_fold_builtin_memory_op, but the reporter
> then found another way to generate such a stmt with UNKNOWN_LOCATION.
>
> I've now gone through gimple_fold_builtin_memory_op looking at all
> statement creation, and found three places in which a new statement
> doesn't have a location set on it (either directly via
> gimple_set_location, or indirectly via gsi_replace), one of which is
> the new reproducer.
>
> This patch adds a gimple_set_location to these three cases, and adds
> test coverage for one of them (the third hunk within the patch), fixing
> the new reproducer for PR analyzer/104308.
>
> Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
>
> OK for trunk in stage 4?  Or in stage 1?

OK for stage4.

> Thanks
> Dave
>
> gcc/ChangeLog:
>         PR analyzer/104308
>         * gimple-fold.cc (gimple_fold_builtin_memory_op): Explicitly set
>         the location of new_stmt in all places that don't already set it,
>         whether explicitly, or via a call to gsi_replace.
>
> gcc/testsuite/ChangeLog:
>         PR analyzer/104308
>         * gcc.dg/analyzer/pr104308.c: Add test coverage.
>
> Signed-off-by: David Malcolm <dmalcolm@redhat.com>
> ---
>  gcc/gimple-fold.cc                       |  3 +++
>  gcc/testsuite/gcc.dg/analyzer/pr104308.c | 13 ++++++++++++-
>  2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
> index ac22adfd9b1..863ee3d3912 100644
> --- a/gcc/gimple-fold.cc
> +++ b/gcc/gimple-fold.cc
> @@ -1048,6 +1048,7 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
>                           gsi_replace (gsi, new_stmt, false);
>                           return true;
>                         }
> +                     gimple_set_location (new_stmt, loc);
>                       gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
>                       goto done;
>                     }
> @@ -1302,6 +1303,7 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
>                                                    new_stmt);
>               gimple_assign_set_lhs (new_stmt, srcvar);
>               gimple_set_vuse (new_stmt, gimple_vuse (stmt));
> +             gimple_set_location (new_stmt, loc);
>               gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
>             }
>           new_stmt = gimple_build_assign (destvar, srcvar);
> @@ -1338,6 +1340,7 @@ set_vop_and_replace:
>           gsi_replace (gsi, new_stmt, false);
>           return true;
>         }
> +      gimple_set_location (new_stmt, loc);
>        gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
>      }
>
> diff --git a/gcc/testsuite/gcc.dg/analyzer/pr104308.c b/gcc/testsuite/gcc.dg/analyzer/pr104308.c
> index 9cd5ee6feee..a3a0cbb7317 100644
> --- a/gcc/testsuite/gcc.dg/analyzer/pr104308.c
> +++ b/gcc/testsuite/gcc.dg/analyzer/pr104308.c
> @@ -1,8 +1,19 @@
> +/* Verify that we have source locations for
> +   -Wanalyzer-use-of-uninitialized-value warnings involving folded
> +   memory ops.  */
> +
>  #include <string.h>
>
> -int main()
> +int test_memmove_within_uninit (void)
>  {
>    char s[5]; /* { dg-message "region created on stack here" } */
>    memmove(s, s + 1, 2); /* { dg-warning "use of uninitialized value" } */
>    return 0;
>  }
> +
> +int test_memcpy_from_uninit (void)
> +{
> +  char a1[5];
> +  char a2[5]; /* { dg-message "region created on stack here" } */
> +  return (memcpy(a1, a2, 5) == a1); /* { dg-warning "use of uninitialized value" } */
> +}
> --
> 2.26.3
>