0001059: Undefined behavior with embedded assignment goes undetected

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Date Submitted

Last Update

0001059

Frama-C

Kernel

public

2012-01-07 17:36

2014-02-12 16:58

Reporter

pascal

Assigned To

virgile

Priority

normal

Severity

major

Reproducibility

always

Status

closed

Resolution

fixed

Platform

OS Version

Product Version

Frama-C Nitrogen-20111001

Target Version

Fixed in Version

Frama-C Oxygen-20120901

Summary

0001059: Undefined behavior with embedded assignment goes undetected

Description

It seems to me that the following program exhibits undefined behavior due to a= and ++a not being separated by a sequence point. int main() { int a = 1; int b = 0; if (a = b || ++a == 2) printf("T: a=%i, b=%i", a, b); else printf("F: a=%i, b=%i", a, b); return 0; } But the following command gives no sign that the undefined behavior is detected: $ bin/toplevel.opt -unspecified-access -val t.c -print [kernel] preprocessing with "gcc -C -E -I. t.c" [value] Analyzing a complete application starting at main [value] Computing initial state [value] Initial state computed [value] Values of globals at initialization [value] computing for function printf <- main. Called from t.c:6. [kernel] warning: No code for function printf, default assigns generated [value] Done for function printf [value] Recording results for main [value] done for function main [value] ====== VALUES COMPUTED ====== [value] Values at end of function main: a ? {1} b ? {0} __retres ? {0} /* Generated by Frama-C */ /*@ behavior generated: assigns \at(\result,Post) \from \nothing; */ extern int ( /* missing proto */ printf)(); int main(void) { int __retres; int a; int b; int tmp; a = 1; b = 0; if (b) { tmp = 1; } else { a ++; if (a == 2) { tmp = 1; } else { tmp = 0; } } a = tmp; if (a) { printf("T: a=%i, b=%i",a,b); } else { printf("F: a=%i, b=%i",a,b); } __retres = 0; return (__retres); }

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Notes
(0002572) pascal (reporter) 2012-01-08 13:41	Note that the condition is parsed (a = (b \|\| ++a == 2)). This much is apparently correct.

(0004619) 2014-02-12 16:58	Fix committed to stable/neon branch.

Issue History
Date Modified	Username	Field	Change
2012-01-07 17:36	pascal	New Issue
2012-01-07 17:36	pascal	Status	new => assigned
2012-01-07 17:36	pascal	Assigned To	=> virgile
2012-01-08 13:41	pascal	Note Added: 0002572
2012-09-05 18:51	svn	Checkin
2012-09-05 18:51	svn	Status	assigned => resolved
2012-09-05 18:51	svn	Resolution	open => fixed
2012-09-19 17:15	signoles	Fixed in Version	=> Frama-C Oxygen-20120901
2012-09-19 17:16	signoles	Status	resolved => closed
2014-02-12 16:58		Note Added: 0004619
2014-02-12 16:58		Status	closed => resolved