[llvm-bugs] [Bug 33299] New: functions with empty body are wrongly optimized
via llvm-bugs
llvm-bugs at lists.llvm.org
Sun Jun 4 05:51:43 PDT 2017
https://bugs.llvm.org/show_bug.cgi?id=33299
Bug ID: 33299
Summary: functions with empty body are wrongly optimized
Product: clang
Version: 4.0
Hardware: Macintosh
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: unassignedclangbugs at nondot.org
Reporter: yangyibiao at nju.edu.cn
CC: llvm-bugs at lists.llvm.org
Created attachment 18571
--> https://bugs.llvm.org/attachment.cgi?id=18571&action=edit
the test file for reproduce this bug
/* test.c */
#include "stdio.h"
static int g;
static int arr[2] = {0, 1};
static int f1()
{
// function with empty body
}
static void f()
{
g = f1();
}
void main(int argc, char **argv)
{
f();
printf("%d\n", arr[g]);
}
/* end of test.c */
With/without optimization when compiling the attached file "test.c", the
outputs are different.
the command for compile the attached file is as follows:
$ clang -O0 test.c -o test0
$ clang -O1 test.c -o test1
$ clang -O2 test.c -o test2
$ clang -O3 test.c -o test3
$ clang -Ofast test.c -o test4
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