Re: Sporadic failures of selftest tests

[Pedro Alves <palves@redhat.com>]

On 10/17/2017 03:40 PM, Pedro Alves wrote:
> On 10/17/2017 03:34 PM, Pedro Alves wrote:
> 
>> Wait, is your build of GDB an optimized build?  Maybe the compiler
>> managed to inline captured_command_loop for you?  Currnetly, when
>> GDB stops for an inline breakpoint, it stops at the stack caller,
>> which would explain this.
> 
> Yup, I can reproduce this with:
> 
> $ rm -f main.o && make CXXFLAGS="-g3 -O2"
> $ make check TESTS="*/complaints.exp"
> [...]
> Running src/gdb/testsuite/gdb.gdb/complaints.exp ...
> FAIL: gdb.gdb/complaints.exp: run until breakpoint at captured_command_loop
> WARNING: Couldn't test self

Ah, and in addition to the wrong function hit, I do also see
the prompt issue then.  Here's what I just saw in a manual run:

(top-gdb) b captured_command_loop
Breakpoint 3 at 0x71ee60: file src/gdb/main.c, line 324.
(top-gdb) r
Starting program: build/gdb/gdb -data-directory=data-directory
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[New Thread 0x7fffed131700 (LWP 4358)]
[New Thread 0x7fffec930700 (LWP 4359)]
[New Thread 0x7fffec12f700 (LWP 4360)]
[New Thread 0x7fffeb92e700 (LWP 4361)]
[New Thread 0x7fffeb12d700 (LWP 4362)]
[New Thread 0x7fffea92c700 (LWP 4363)]
[New Thread 0x7fffea12b700 (LWP 4364)]
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(gdb)                  <<<<<< PROMPT HERE
Thread 1 "gdb" hit Breakpoint 3, captured_main (data=<optimized out>) at src/gdb/main.c:1147
1147              captured_command_loop ();
(top-gdb) 

Note the "PROMPT HERE" line.

So indeed, that inferior gdb prompt can confuse gdb_test_multiple.
That prompt is only output in optimized builds, because in that
case, due to inlining, the breakpoint happens to trigger _after_
captured_command_loop prints the prompt...  In non-optimized builds,
the prompt is _not_ output.

Thanks,
Pedro Alves