--with-pydebug default compiler flags is a trade-off between "runtime checks for debug" and performance. -O0 makes Python slower. For example, we want to Python CI to run as fast as possible.
I don't want to fight for https://bugs.python.org/issue38350 I simply learnt to type: ./configure --with-pydebug CFLAGS="-O0" (I have a shell alias for that). Victor On Mon, May 24, 2021 at 5:54 PM Guido van Rossum <gu...@python.org> wrote: > > I'm confused. I've always assumed that --with-pydebug was intended for the > situation where you're modifying the C code, so obviously you might have to > debug C code. (I know that was the case when we introduced it, decades ago.) > If that's not the goal, then what is --py-debug used for? > > On Mon, May 24, 2021 at 3:35 AM Victor Stinner <vstin...@python.org> wrote: >> >> "Debugging" means many things. Python is built with -Og because it >> makes Python faster than -O0, and most developers debug Python code, >> not C code (in gdb). >> >> If you don't need to go up to the gdb/lldb level, -Og is fine. >> >> It would even make sense to build Python with -O3 in debug mode if you >> don't debug C code at all, only pure Python code. >> >> My proposition to switch to -00 by default was rejected: >> https://bugs.python.org/issue38350 >> >> I also love -O0 when I modify C code because it makes the build faster ;-) >> >> Fedora Python debug builds are now built with -O0 which makes gdb a >> way more pleasant experience, not more strange behavior with inlined >> code or "<optimized out>" local variables or function arguments. >> >> Victor >> >> On Sun, May 23, 2021 at 3:57 PM Skip Montanaro <skip.montan...@gmail.com> >> wrote: >> > >> > > I strongly suggest to only build Python with -O0 when using gdb. -Og >> > > enables too many optimizations which makes gdb less usable. >> > >> > Thanks, Victor. It never made sense to me that you would want any >> > optimizations enabled when truly debugging code (as opposed to wanting >> > debug symbols and a sane traceback in production code). >> > >> > I'm getting more convinced that the problem I'm seeing is a GCC/GDB >> > thing, particularly because I can move the erroneous stopping point by >> > changing the GCC optimization level. I'll probably open a bugzilla >> > report just so it's on that team's radar screen. In the meantime, to >> > get going again I wrote a crude script which maps the >> > file:function:label form to file:linenumber form. That way I can >> > save/restore breakpoints across GDB sessions and still avoid problems >> > when the offsets to specific instructions change. >> > >> > Skip >> > >> > Skip >> >> >> >> -- >> Night gathers, and now my watch begins. It shall not end until my death. >> _______________________________________________ >> Python-Dev mailing list -- python-dev@python.org >> To unsubscribe send an email to python-dev-le...@python.org >> https://mail.python.org/mailman3/lists/python-dev.python.org/ >> Message archived at >> https://mail.python.org/archives/list/python-dev@python.org/message/FPWJHHV55JPF6ZQVI2OGMYSIPYN3AXH2/ >> Code of Conduct: http://python.org/psf/codeofconduct/ > > > > -- > --Guido van Rossum (python.org/~guido) > Pronouns: he/him (why is my pronoun here?) -- Night gathers, and now my watch begins. It shall not end until my death. _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/G7EFOMH7DXC3TUCR3R6UJ7Q2KTT5UN22/ Code of Conduct: http://python.org/psf/codeofconduct/
