https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97196
Bug ID: 97196
Summary: Difference in output between no optimization and -O2,
triggered by a variable wrapped in parentheses in the
RHS of the assignment operator
Product: gcc
Version: 9.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: m.bartelsman.mejia at student dot rug.nl
Target Milestone: ---
Created attachment 49266
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49266&action=edit
Source and preprocessed files
GCC version:
9.3.0
System:
Ubuntu 20.04.1 LTS on WSL2 on Win10 x86_64, and at least one other,
unknown, system.
GCC Options:
gcc -std=c99 -pedantic -Wall -o a.out *.c
gcc -std=c99 -pedantic -Wall -o a.out *.c -O2
How to reproduce:
On both versions run:
$ a.out
$ 2000
Non -O2 will yield `2002 3`, while -O2 will yield `2002 0`
Compiler output:
Only on -O2 version:
palindromicSums.c: In function ‘main’:
palindromicSums.c:34:3: warning: ignoring return value of ‘scanf’, declared
with attribute warn_unused_result [-Wunused-result]
34 | scanf("%d", &n);
| ^~~~~~~~~~~~~~~
