[Bug c/103103] New: Incorrect integer optimization omits x < 0 comparison
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103103 Bug ID: 103103 Summary: Incorrect integer optimization omits x < 0 comparison Product: gcc Version: 11.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: k.melekhin at gmail dot com Target Milestone: --- Created attachment 51739 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51739&action=edit Simple test program + version info On higher optimization levels O2,O3 the following code omits the "newsz < 0" comparison, likely due to invalid optimization / assumtion that value will never change and always be 0, however this is incorrect. See attachment, shows very simple test to reproduce. Also my gcc version included in that file comment. Gcc's output with -O0 is correct. Tested with other C compilers and they generate correct output on any optimization level.
[Bug c/103103] Incorrect integer optimization omits x < 0 comparison
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103103 --- Comment #3 from Kyryl Melekhin --- Thank you! I figured that this has something to do with being UB behavior with int overflow, however it's strange to find this kind of bug only on 1 compiler, with no possible warnings or idications that something is wrong. Perhaps a warning of UB into overflow from compiler be nice. Have a good day.
[Bug c/103111] New: bogus stringop overflow warning
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103111 Bug ID: 103111 Summary: bogus stringop overflow warning Product: gcc Version: 11.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: k.melekhin at gmail dot com Target Milestone: --- Created attachment 51743 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51743&action=edit test sample Hello, please see the attachment. Why is this warning being generated, it is clearly seen that there will only be 1 allocation and savepath->s_n is being set to 0. I know if I use unsigned values warning goes away, but this warning still seems not right, because in this case we are not even dealing with anything close to being considered integer overflow. I think this is a gcc bug, my appologies if this is known bug there seems to be some similar open for c++ but not sure.
