https://bugs.kde.org/show_bug.cgi?id=487296
Bug ID: 487296
Summary: --track-fds=yes and --track-fds=all report erroneous
information when fds 0, 1, or 2 are used as non-std
Classification: Developer tools
Product: valgrind
Version: 3.24 GIT
Platform: Other
OS: Other
Status: REPORTED
Severity: minor
Priority: NOR
Component: memcheck
Assignee: jsew...@acm.org
Reporter: imb2...@columbia.edu
Target Milestone: ---
Created attachment 169667
--> https://bugs.kde.org/attachment.cgi?id=169667&action=edit
patch to accurately report leaks for fds 0, 1, 2
SUMMARY
If a program closes any std fd then reopens it as non-std, Memcheck's
--track-fds=yes report is inaccurate. If fds 0, 1, or 2 are in use,
--track-fds=yes and --track-fds=all treat them as std (regardless of whether
they are or not), leading to erroneous output. Leak messages are consequently
omitted with --track-fds=yes.
STEPS TO REPRODUCE
Run a program that closes one of the std fds, and reopens another file in its
place without closing it:
// test.c
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
int main(void) {
FILE *fp;
assert(fclose(stdout) == 0);
fp = fopen("newfile.txt", "w");
assert(fileno(fp) == STDOUT_FILENO);
return 0;
}
OBSERVED RESULT
$ gcc -g -Wall test.c -o test && valgrind --leak-check=yes --track-fds=yes
./test
==422217== Memcheck, a memory error detector
==422217== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==422217== Using Valgrind-3.24.0.GIT and LibVEX; rerun with -h for copyright
info
==422217== Command: ./test
==422217==
==422217==
==422217== FILE DESCRIPTORS: 3 open (3 std) at exit.
==422217==
==422217== HEAP SUMMARY:
==422217== in use at exit: 472 bytes in 1 blocks
==422217== total heap usage: 1 allocs, 0 frees, 472 bytes allocated
==422217==
==422217== LEAK SUMMARY:
==422217== definitely lost: 0 bytes in 0 blocks
==422217== indirectly lost: 0 bytes in 0 blocks
==422217== possibly lost: 0 bytes in 0 blocks
==422217== still reachable: 472 bytes in 1 blocks
==422217== suppressed: 0 bytes in 0 blocks
==422217== Reachable blocks (those to which a pointer was found) are not shown.
==422217== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==422217==
==422217== For lists of detected and suppressed errors, rerun with: -s
==422217== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
Note that Memcheck reports 3 std fds open at exit, does not report a leak
message, and does not report any errors.
EXPECTED RESULT
Memcheck should report 2 std fds open at exit, a leak message should be
outputted for the newly opened fd, and the error summary should list 1 error.
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