[v1.2] fortify: Fix spurious warning with realpath

  The length and object size arguments were swapped around for realpath.
Also add a smoke test so that any changes in this area get caught in
future.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
Changes from v1.1:
- It's *The* GNU Toolchain Authors, not GNU Toolchain Authors.

Changes from v1:
- It's the GNU *Toolchain* Authors, not GNU Tools Authors.

 debug/Makefile           |  3 ++-
 debug/tst-realpath-chk.c | 37 +++++++++++++++++++++++++++++++++++++
 stdlib/bits/stdlib.h     |  2 +-
 3 files changed, 40 insertions(+), 2 deletions(-)
 create mode 100644 debug/tst-realpath-chk.c
  

On 12/17/21 07:26, Siddhesh Poyarekar via Libc-alpha wrote:
> The length and object size arguments were swapped around for realpath.
> Also add a smoke test so that any changes in this area get caught in
> future.
> 
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> ---
> Changes from v1.1:
> - It's *The* GNU Toolchain Authors, not GNU Toolchain Authors.
> 
> Changes from v1:
> - It's the GNU *Toolchain* Authors, not GNU Tools Authors.
> 
>   debug/Makefile           |  3 ++-
>   debug/tst-realpath-chk.c | 37 +++++++++++++++++++++++++++++++++++++
>   stdlib/bits/stdlib.h     |  2 +-
>   3 files changed, 40 insertions(+), 2 deletions(-)
>   create mode 100644 debug/tst-realpath-chk.c
> 
> diff --git a/debug/Makefile b/debug/Makefile
> index 357f888246..bc37e466ee 100644
> --- a/debug/Makefile
> +++ b/debug/Makefile
> @@ -108,6 +108,7 @@ CFLAGS-tst-longjmp_chk2.c += -fexceptions -fasynchronous-unwind-tables
>   CPPFLAGS-tst-longjmp_chk2.c += -D_FORTIFY_SOURCE=1
>   CFLAGS-tst-longjmp_chk3.c += -fexceptions -fasynchronous-unwind-tables
>   CPPFLAGS-tst-longjmp_chk3.c += -D_FORTIFY_SOURCE=1
> +CPPFLAGS-tst-realpath-chk.c += -D_FORTIFY_SOURCE=2
>   
>   # We know these tests have problems with format strings, this is what
>   # we are testing.  Disable that warning.  They are also testing
> @@ -155,7 +156,7 @@ tests = backtrace-tst tst-longjmp_chk tst-chk1 tst-chk2 tst-chk3 \
>   	tst-lfschk1 tst-lfschk2 tst-lfschk3 test-strcpy_chk test-stpcpy_chk \
>   	tst-chk4 tst-chk5 tst-chk6 tst-chk7 tst-chk8 tst-lfschk4 tst-lfschk5 \
>   	tst-lfschk6 tst-longjmp_chk2 tst-backtrace2 tst-backtrace3 \
> -	tst-backtrace4 tst-backtrace5 tst-backtrace6
> +	tst-backtrace4 tst-backtrace5 tst-backtrace6 tst-realpath-chk
>   
>   ifeq ($(have-ssp),yes)
>   tests += tst-ssp-1
> diff --git a/debug/tst-realpath-chk.c b/debug/tst-realpath-chk.c
> new file mode 100644
> index 0000000000..b10f9a11b1
> --- /dev/null
> +++ b/debug/tst-realpath-chk.c
> @@ -0,0 +1,37 @@
> +/* Smoke test to verify that realpath does not cause spurious warnings.
> +   Copyright (C) The GNU Toolchain Authors.

I need to remove (C) here to be consistent with gcc.

> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <limits.h>
> +#include <stdlib.h>
> +
> +#include <support/check.h>
> +#include <support/support.h>
> +
> +static int
> +do_test (void)
> +{
> +#if PATH_MAX > 0
> +  char buf[PATH_MAX + 1];
> +  char *res = realpath (".", buf);
> +  TEST_VERIFY (res == buf);
> +#endif
> +
> +    return 0;
> +}
> +
> +#include <support/test-driver.c>
> diff --git a/stdlib/bits/stdlib.h b/stdlib/bits/stdlib.h
> index 067115eeca..ccacbdf76a 100644
> --- a/stdlib/bits/stdlib.h
> +++ b/stdlib/bits/stdlib.h
> @@ -42,7 +42,7 @@ __NTH (realpath (const char *__restrict __name, char *__restrict __resolved))
>       return __realpath_alias (__name, __resolved);
>   
>   #if defined _LIBC_LIMITS_H_ && defined PATH_MAX
> -  if (__glibc_unsafe_len (sz, sizeof (char), PATH_MAX))
> +  if (__glibc_unsafe_len (PATH_MAX, sizeof (char), sz))
>       return __realpath_chk_warn (__name, __resolved, sz);
>   #endif
>     return __realpath_chk (__name, __resolved, sz);
>