Re: [PATCH] Fix selftest::read_file for empty file

[Marek Polacek]

On Wed, Jul 19, 2017 at 10:49:33AM -0400, David Malcolm wrote:
> selftest::read_file currently assumes it has a non-empty file;
> when loading an empty file it dies with an assertion failure,
> or a write through NULL if assertions are disabled.
> 
> This patch fixes this case, removing this limitation.
> 
> Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu;
> takes -fself-test from 39458 passes to 39460.
> 
> OK for trunk?
> 
> gcc/ChangeLog:
>       * selftest.c (selftest::read_file): Handle 0-length files.
>       (selftest::test_read_empty_file): New function.
>       (selftest::selftest_c_tests): Call it.
> ---
>  gcc/selftest.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/gcc/selftest.c b/gcc/selftest.c
> index b41b9f5..026a35f 100644
> --- a/gcc/selftest.c
> +++ b/gcc/selftest.c
> @@ -192,7 +192,14 @@ read_file (const location &loc, const char *path)
>    fclose (f_in);
>  
>    /* 0-terminate the buffer.  */
> +  if (total_sz == 0)
> +    {
> +      size_t new_alloc_sz = alloc_sz ? alloc_sz * 2: total_sz + 1;

There should be a space before ":".  Also, if you know total_sz is 0, why
"total_sz + 1" and not just "1"?

> +      result = (char *)xrealloc (result, new_alloc_sz);

A space after ).

> +      alloc_sz = new_alloc_sz;
> +    }
>    gcc_assert (total_sz < alloc_sz);
> +  gcc_assert (result);
>    result[total_sz] = '\0';
>  
>    return result;
> @@ -296,6 +303,17 @@ test_read_file ()
>    free (buf);
>  }
>  
> +/* Verify that read_file can cope with an empty file.  */
> +
> +static void
> +test_read_empty_file ()
> +{
> +  temp_source_file t (SELFTEST_LOCATION, "empty.txt", "");
> +  char *buf = read_file (SELFTEST_LOCATION, t.get_filename ());
> +  ASSERT_STREQ ("", buf);
> +  free (buf);
> +}
> +
>  /* Verify locate_file (and read_file).  */
>  
>  static void
> @@ -317,6 +335,7 @@ selftest_c_tests ()
>    test_assertions ();
>    test_named_temp_file ();
>    test_read_file ();
> +  test_read_empty_file ();
>    test_locate_file ();
>  }
>  
> -- 
> 1.8.5.3
> 

        Marek