0000733: Invalid results in presence of pseudo-recursive calls in inout and from

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Date Submitted

Last Update

0000733

Frama-C

Plug-in > inout

public

2011-02-20 19:16

2017-05-31 19:05

Reporter

yakobowski

Assigned To

yakobowski

Priority

normal

Severity

minor

Reproducibility

always

Status

closed

Resolution

fixed

Platform

OS Version

Product Version

Frama-C Carbon-20110201

Target Version

Fixed in Version

Frama-C 15 Phosphorus

Summary

0000733: Invalid results in presence of pseudo-recursive calls in inout and from

Description

The Inout and From plugins are apparently designed to handle "pseudo" recursive calls, ie. when the value analysis does not detect a recursive call, but the plugin see a circularity in the stacks of examined functions. However, they are all buggy, because of the way the results are cached.

Indeed, when a circularity is encountered, the analysis is stopped immediately. This means that the results for the first function in the cycle is correct, but not those for the intermediate functions.

This can be seen with the example file: the inputs (option -input) for function h2 should include x.

Additional Information

Commit 12050 has removed most of the warnings the plugins printed unnecessarily when those pseudo recursive calls were encountered, so the error can now be completely silent (however, even with the warnings the plugins were buggy, as they implied that the analysis was correct if the value analysis was happy).

I have some (quite obvious) suggestions for correcting the bug, but they are not very efficient wrt to time complexity. Suggestions are welcome.

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No tags attached.

Attached Files

recursion2.i [^] (239 bytes) 2011-02-20 19:16 [Show Content] [Hide Content]

/*run.config
  OPT: -journal-disable -input -val
 */
int x, y;

void h2 (int);
void h1 (int);

void h1 (int i) {
  int r = x;
  if (i)
    h2 (i);
}
void h2 (int i) {
  int r = y;
  if (!i)
    h1 (i);
}

void main() {
  h2(0);
  h1(1);
}

Relationships

Notes
(0001527) pascal (reporter) 2011-02-20 21:09	1/ I know. 2/ From my point of view any sort of recursion (that is, any cycle in the syntactic call graph) is unsupported in the value analysis and derived analyses. Perhaps I should assign the bug to you so that you feel free to do what's necessary (as long as you don't break what works for programs without recursion)?

(0001671) yakobowski (manager) 2011-03-31 21:59	Bug remains in From and Operation_inputs plugins.

(0006391) yakobowski (manager) 2017-03-31 20:17	No longer relevant in Phosphorus, where -inout-callwise is set by default.

Issue History
Date Modified	Username	Field	Change
2011-02-20 19:16	yakobowski	New Issue
2011-02-20 19:16	yakobowski	Status	new => assigned
2011-02-20 19:16	yakobowski	Assigned To	=> pascal
2011-02-20 19:16	yakobowski	File Added: recursion2.i
2011-02-20 21:09	pascal	Note Added: 0001527
2011-02-22 01:08	yakobowski	Assigned To	pascal => yakobowski
2011-02-23 11:00	svn	Checkin
2011-03-31 21:59	yakobowski	Note Added: 0001671
2011-03-31 21:59	yakobowski	Status	assigned => acknowledged
2013-06-11 23:10	yakobowski	Severity	major => minor
2017-03-31 20:17	yakobowski	Note Added: 0006391
2017-03-31 20:17	yakobowski	Status	acknowledged => resolved
2017-03-31 20:17	yakobowski	Resolution	open => fixed
2017-05-31 19:04	signoles	Fixed in Version	=> Frama-C 15 Phosphorus
2017-05-31 19:05	signoles	Status	resolved => closed