[Bug tree-optimization/90949] [9/10 Regression] null pointer check removed

[luk32 at o2 dot pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90949

Łukasz Kucharski  changed:

   What|Removed |Added

 CC||luk32 at o2 dot pl

--- Comment #5 from Łukasz Kucharski  ---
Hi, I am the guy who isolated the issue for c++, behind the question.

If this isn't too much, could anyone explain why does changing type of cleanup
from int to bool solves the issue?

Everything else I can understand, because those are changes in observable
behaviour.

Do the optimizers treat boolean and integers differently, even in bool
contexts? This is intriguing.

I know this is tangential, but it really bugs me and I am not sure if I can
study the sourcecode of gcc optimizer in reasonable time.

[Bug c++/87068] New: No diagnostic on an ill-formed [[fallthrough]]

[luk32 at o2 dot pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87068

Bug ID: 87068
   Summary: No diagnostic on an ill-formed [[fallthrough]]
   Product: gcc
   Version: unknown
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: luk32 at o2 dot pl
  Target Milestone: ---

gcc cleanly compiles an ill-formed [[fallthrough]] example from the standard,
producing no diagnostic. I believe it's a bug.

Problematic code:

// http://eel.is/c++draft/dcl.attr.fallthrough
void f(int n) {
  void g(), h(), i();
  switch (n) {
  case 1:
  case 2:
g();
[[fallthrough]];
  case 3:   // warning on fallthrough discouraged
h();
  case 4:   // implementation may warn on fallthrough
i();
[[fallthrough]];// ill-formed
  }
}

Live example https://godbolt.org/z/fftSM-
Credit:
https://stackoverflow.com/questions/51983560/should-there-be-a-diagnostic-from-from-gcc-for-this-ill-formed-c-code

[Bug inline-asm/62144] "Frame pointer required, but reserved" error with -fomit-frame-pointer but only with -m32 -O2

[luk32 at o2 dot pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62144

Łukasz Kucharski  changed:

   What|Removed |Added

 CC||luk32 at o2 dot pl

--- Comment #5 from Łukasz Kucharski  ---
Created attachment 33833
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33833&action=edit
Example program that fails compilation with optimization enabled.

[Bug inline-asm/62144] "Frame pointer required, but reserved" error with -fomit-frame-pointer but only with -m32 -O2

[luk32 at o2 dot pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62144

--- Comment #6 from Łukasz Kucharski  ---
Comment on attachment 33833
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33833
Example program that fails compilation with optimization enabled.

Hello, 

I believe we run into the same problem, however we extracted example that
doesn't need `-m32`. Just `-O2` breaks the build. gcc-4.8 passed with no
problems.

With regards,
luk32.

[Bug inline-asm/62144] "Frame pointer required, but reserved" error with -fomit-frame-pointer but only with -m32 -O2

[luk32 at o2 dot pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62144

--- Comment #8 from Łukasz Kucharski  ---
Jakub,

fair enough. However, changing the optimization level should not break the
compilation. The issue is, at least for me, is not that we can't omit the frame
pointer, but that it depends on the optimization level.

I couldn't find anything in the docs, which would allow such behaviour. Maybe I
missed it. Anyway, IMO at most a warning should be issued that a potential
optimization conflicts with the flag.

With regards,
luk32.