Re: [PATCH] gdb/testsuite: Fix race in gdb.dwarf2/calling-convention.exp

[Bruno Larsen <blarsen@redhat.com>]

On 3/30/22 09:50, Lancelot SIX via Gdb-patches wrote:
> Pedro Alves warned me that there is a race in
> gdb.dwarf2/calling-convention.exp making the test sometimes fail on his
> setup.  This can be reliably reproduced using :
> 
>      make check-read1 TESTS="gdb.dwarf2/calling-convention.exp"
> 
> The relevant part of the gdb.log file is:
> 
>      return 35
>      Function 'foo' does not follow the target calling convention.
>      If you continue, setting the return value will probably lead to unpredictable behaviors.
>      Make foo return now? (y or n) PASS: gdb.dwarf2/calling-convention.exp: return 35
>      n
>      Not confirmed
>      (gdb) FAIL: gdb.dwarf2/calling-convention.exp: finish
> 
> The issue is that when doing the test for "return 35", the DejaGnu test
> sends "n" (to tell GDB not to perform the return action) but never
> consumes the "Not confirmed" acknowledgment sent by GDB.  Later, when
> trying to do the next test, DejaGnu tries to match the leftover output
> from the "return" test. As this output is not expected, the test fails.
> 
> Fix this by consuming the "Not confirmed\r\n$gdb_prompt " output.
> 
> While at cleaning up this test, also improve the regex for the return
> test:
> - Remove the leading ".*" pattern.
> - Replace the "$" (end of line marker) with "\$" because it does not
>    identify a TCL variable.
> 
> Tested on x86_64-gnu-linux, using
> 
> - make check TESTS="gdb.dwarf2/calling-convention.exp"
> - make check-read1 TESTS="gdb.dwarf2/calling-convention.exp"
> 
> Change-Id: I42858b13db2cbd623c5c1739de65ad423e0c0938

Thanks for looking at this! It had me quite confused. The change and explanation looks good to me, but I can't approve patches.
> ---
>   gdb/testsuite/gdb.dwarf2/calling-convention.exp | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/gdb/testsuite/gdb.dwarf2/calling-convention.exp b/gdb/testsuite/gdb.dwarf2/calling-convention.exp
> index 0a11cb15c68..7ea9ae7c768 100644
> --- a/gdb/testsuite/gdb.dwarf2/calling-convention.exp
> +++ b/gdb/testsuite/gdb.dwarf2/calling-convention.exp
> @@ -84,9 +84,9 @@ gdb_breakpoint "foo"
>   gdb_continue_to_breakpoint "foo"
>   
>   gdb_test_multiple "return 35" "" {
> -    -re ".*Function 'foo' does not follow the target calling convention.\r\nIf you continue, setting the return value will probably lead to unpredictable behaviors.\r\nMake foo return now?.*\\(y or n\\) $" {
> -	send_gdb "n\n"
> +    -re "Function 'foo' does not follow the target calling convention.\r\nIf you continue, setting the return value will probably lead to unpredictable behaviors.\r\nMake foo return now?.*\\(y or n\\) \$" {
>   	pass $gdb_test_name
> +	gdb_test "n" "Not confirmed" "Cancel return"
>       }
>   }
>   
> 
> base-commit: 5321c31bc78379a33f07dc7bef9256d05b942ad7


-- 
Cheers!
Bruno Larsen