[LLVMbugs] [Bug 17990] New: may wrong code bug at -O0 level

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17990

            Bug ID: 17990
           Summary: may wrong code bug at -O0 level
           Product: clang
           Version: 3.3
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: justmao945 at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 11567
  --> http://llvm.org/bugs/attachment.cgi?id=11567&action=edit
source

Sorry for I don't know where to post this bug, so I put it here as the "NEW".
Thanks.


Source code:
------------------------------------------
#include <ctype.h>
#include <stdio.h>
int main() {
    const char* str = "abcd1234abcd12333";
    for(size_t i = 0; i < 10; ++i) {
        char c = str[i];
        bool d = isdigit(c);  // Clang store str[0] to d, volatile doesn't help
        if(i < 10 && d == isdigit(str[i]) ) {
            printf("%zu %c\n", i, str[i]);
        }
    }
    return 0;
}
------------------------------------------

Compilation and run
------------------------------------------
ohio:tmp$clang -O0 bug.cc
ohio:tmp$./a.out
0 a
1 b
2 c
3 d
8 a
9 b
ohio:tmp$clang -O1 bug.cc
ohio:tmp$./a.out
0 a
1 b
2 c
3 d
4 1
5 2
6 3
7 4
8 a
9 b

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