Re: [PATCH] Fix -Wstring-compare testcase build failure

[Pedro Alves <palves@redhat.com>]

On 6/23/20 3:57 PM, Gary Benson via Gdb-patches wrote:
> Hi all,
> 
> Clang fails to compile the file gdb/testsuite/gdb.cp/try_catch.cc
> with the following error:
>   warning: result of comparison against a string literal is
>   unspecified (use strncmp instead) [-Wstring-compare]
> 
> This patch replaces the string literal with a pointer, to avoid
> the error.
> 
> Is it ok to commit?

Hmm, no, I don't think so.

>  
>    // 3 use standard library
>    using namespace std;
> +  const char *throwme = "gdb.1";
>    try
>      {
>        if (j < 100)
> -	throw invalid_argument("gdb.1"); // marker 3-throw
> +	throw invalid_argument(throwme); // marker 3-throw
>      }
>    catch (exception& obj)
>      {
> -      if (obj.what() != "gdb.1")	// marker 3-catch
> +      if (obj.what() != throwme)	// marker 3-catch
>  	test &= false;
>      }
>    return 0;
invalid_argument stores a copy of the string, so with or
without your patch, that (obj.what() != "gdb.1") comparison
is returning false.  Thus the "test &= false;" statement is
executing.

IOW, that Clang warning found a bug in the test program...

The fix should be to use strcmp instead.

And also, please add a market at the "return 0;" line,
let the program run to it, and then add a gdb_test checking
that "test" is still true at that point.

Thanks,
Pedro Alves