Re: [PATCH 11/11] explicitly test for stderr in gdb.base/dprintf.exp

[Pedro Alves <pedro@palves.net>]

On 2022-01-26 19:50, Bruno Larsen via Gdb-patches wrote:
> Not all compilers explicitly add stderr information when compiling a

It helps if you say "debug information" instead of just "information".

> program, so to avoid an unrelated failure, we explicitly test to see if
> the compiler has added information about it at all. This was done
> thinking specifically about clang, since it doesn't add stderr
> information and developers treat it as a feature.

Please include a snippet of the failure in the commit log.

I ran the test locally against clang, and I do see a failure here too:

 (gdb) PASS: gdb.base/dprintf.exp: call: fprintf: set dprintf style to call
 continue
 Continuing.
 kickoff 1234
 also to stderr 1234
 'stderr' has unknown type; cast it to its declared type
 (gdb) FAIL: gdb.base/dprintf.exp: call: fprintf: 1st dprintf (timeout)

However, when I debug the program manually, I see that gdb is able to print stderr,
if you run to main first:

 (gdb) p stderr
 'stderr' has unknown type; cast it to its declared type
 (gdb) start
 Temporary breakpoint 1 at 0x4011f6: file ../../../src/gdb/testsuite/gdb.base/dprintf.c, line 35.
 Starting program: /home/pedro/rocm/gdb/build/gdb/testsuite/outputs/gdb.base/dprintf/dprintf 

 Temporary breakpoint 1, main (argc=1, argv=0x7fffffffdc18) at ../../../src/gdb/testsuite/gdb.base/dprintf.c:35
 35        int loc = 1234;
 (gdb) p stderr
 $1 = (FILE *) 0x7ffff7e4e5c0 <_IO_2_1_stderr_>

So... it doesn't seem like the premise of the patch is correct, for the testcase
runs to main -- see the "restart" call in the context of your patch, just below.
Seems like something else may be going on?  Why is GDB not finding the debug info for
stderr in the dprintf call, while manually it is able to find it?

Pedro Alves

> ---
>  gdb/testsuite/gdb.base/dprintf.exp | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/gdb/testsuite/gdb.base/dprintf.exp b/gdb/testsuite/gdb.base/dprintf.exp
> index 0b209c02a62..e214531f6dc 100644
> --- a/gdb/testsuite/gdb.base/dprintf.exp
> +++ b/gdb/testsuite/gdb.base/dprintf.exp
> @@ -111,6 +111,16 @@ proc test_call {} {
>  	test_dprintf "At foo entry.*arg=1235, g=2222\r\n" "2nd dprintf"
>      }
>  
> +    gdb_test_multiple "print stderr" "stderr symbol check" {
> +	-re "\\'stderr\\' has unknown type.*" {
> +	    untested "No information available for stderr, exiting early"
> +	    return
> +	}
> +	-re "\\\$1.*" {
> +	    pass "stderr is available"
> +	}
> +    }
> +
>      with_test_prefix "fprintf" {
>  	restart
>