https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110530
Bug ID: 110530
Summary: Local variable unexpectedly assigned to zero during
passing as an argument
Product: gcc
Version: 11.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: haiqingzhao at microsoft dot com
Target Milestone: ---
Created attachment 55462
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55462&action=edit
This source file reproduces the issue occurring under -Os optimization
1) GCC version: 11.3.0
2) System type: ubuntu 22.04.1
3) Option given: -Os
4) The complete command line that triggers the bug:
i. gcc -Os test.c -o test.o
ii. ./test.o
5) No compiler output error messages or warning messages
6) No pre-processed files
7) Description:
The behaviour of the source file (test.c) works normally under gcc version
9.4.0 no matter if "-Os optimization" is enabled or not. It works still
normally under gcc version 11.3.0 with no optimization enabled, but prints
error message when "-Os optimization" is enabled.
During debugging, it is found that the value of the local variable "size"
is unexpectedly assigned to zero inside the function "process_data" before
calling the function "get_data" at line 18.
It looks like the initialization for the local variable "size" at line 27
is executed after calling the function "get_data" at line 29.
8) Experiment has been done:
i. The source code works normally if the type for the local variable "size"
is changed from unsigned int to unsigned long
