Re: [Qemu-devel] Should configure --enable-debug add -Og to CFLAGS?

[Markus Armbruster <armbru@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 27/06/19 17:43, Markus Armbruster wrote:
>> The fine manual advises:
>> 
>> '-O0'
>>      Reduce compilation time and make debugging produce the expected
>>      results.  This is the default.
>> [...]
>> '-Og'
>>      Optimize debugging experience.  '-Og' should be the optimization
>>      level of choice for the standard edit-compile-debug cycle, offering
>>      a reasonable level of optimization while maintaining fast
>>      compilation and a good debugging experience.  It is a better choice
>>      than '-O0' for producing debuggable code because some compiler
>>      passes that collect debug information are disabled at '-O0'.
>> 
>> Our configure --enable-debug effectively picks -O0.  Should it pick -Og
>> instead?
>> 
>
>     commit 48e56d503e18bd1e8a75463fd7cc1580bf7e7650
>     Author: Paolo Bonzini <pbonzini@redhat.com>
>     Date:   Tue Mar 6 11:32:44 2018 +0100
>
>     Revert "build-sys: compile with -Og or -O1 when --enable-debug"
>
>     This reverts commit 906548689e37ab6cca1e93b3f8d9327a4e17e8af.
>     Even with -Og, the debug experience is noticeably worse
>     because gdb shows a lot more "<optimised out>" variables and
>     function arguments.
>
>     Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>
> :(

Aha, GCC's documentation is more aspirational than factual here.
Nevermind!