facebook/infer

fclose builtin not modeled as file resource

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#556 opened on Jan 6, 2017

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Description

I noticed that the resource predicate for fclose matches Rmemory Mnew instead of Rfile as expected (PredSymb.re). fclose is modeled as free, but no file attribute is set (compare https://github.com/facebook/infer/blob/master/infer/models/c/src/libc_basic.c#L485 and fopen https://github.com/facebook/infer/blob/master/infer/models/c/src/libc_basic.c#L445).

Is there a particular reason for this? If I set the file attribute for fclose, the OCaml type matches the Rfile that I expect. I.e.,

int fclose(FILE* stream) {                                                          
  int n;                                                                            
  free(stream);                                                                     
  __set_file_attribute(stream);                                                     
  n = __infer_nondet_int();                                                         
  if (n > 0)                                                                        
    return 0;                                                                       
  else                                                                              
    return EOF;                                                                     
}

Same question for the close model.

Contributor guide

Research direction
Examine the implementation of fclose in infer/models/c/src/libc basic.c and compare with fopen to understand the missing file attribute. Check PredSymb.re to see how resource predicates are defined. Then add set file attribute(stream) in fclose and test with a simple C program. Also consider applying the same fix to the close model.
Tech stack
c
Domain
tooling
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
basic Cfamiliarity with Infer's modeling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50