Bug 1878600
| Summary: | -fanalyzer -Wanalyzer-file-leak false-positive if FILE is casted to void * | ||||||
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| Product: | [Fedora] Fedora | Reporter: | Daiki Ueno <dueno> | ||||
| Component: | gcc | Assignee: | Dave Malcolm <dmalcolm> | ||||
| Status: | CLOSED UPSTREAM | QA Contact: | Fedora Extras Quality Assurance <extras-qa> | ||||
| Severity: | unspecified | Docs Contact: | |||||
| Priority: | unspecified | ||||||
| Version: | 32 | CC: | aoliva, dmalcolm, fweimer, jakub, jwakely, law, mpolacek, msebor, nickc, sipoyare | ||||
| Target Milestone: | --- | ||||||
| Target Release: | --- | ||||||
| Hardware: | Unspecified | ||||||
| OS: | Unspecified | ||||||
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| Fixed In Version: | Doc Type: | If docs needed, set a value | |||||
| Doc Text: | Story Points: | --- | |||||
| Clone Of: | Environment: | ||||||
| Last Closed: | 2020-09-14 16:31:18 UTC | Type: | Bug | ||||
| Regression: | --- | Mount Type: | --- | ||||
| Documentation: | --- | CRM: | |||||
| Verified Versions: | Category: | --- | |||||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |||||
| Cloudforms Team: | --- | Target Upstream Version: | |||||
| Embargoed: | |||||||
| Attachments: |
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Why would a routine that expects to work with FILE * pass void * instead? Is the routine meant to handle different output mechanisms at the same time? Otherwise it makes no sense to me. Yes, the routine can also take a string and the user supplied callback ("reader") is responsible for the cast. It's the design of the upstream project we copy so we don't want to let the code diverge from it:
https://github.com/benhoyt/inih
These lines:
return ini_parse_stream((ini_reader)fgets, file);
and
while (reader(line, max_line, stream) != NULL)
are undefined because the called fgets function does not have the type that is used to call it. (I don't know if this is what confuses the analyzer.)
In order to make this find, you need to define a wrapper function of the correct type that calls fgets, instead of the cast to ini_reader.
Thanks for filing this bug report. The leak diagnostic does look like a false positive to me. I've tested it with gcc 10.2 and with upstream git "master" (for gcc 11). I can reproduce it with gcc 10.2. gcc 11 is no longer affected: https://godbolt.org/z/df3G6o It was probably fixed by the big rewrite of state-handling (upstream commit r11-2694-g808f4dfeb3a95f50f15e71148e5c1067f90a126d). I'll look at adding this case to the upstream regression test suite for -fanalyzer, and then close this out as UPSTREAM. Regression test committed upstream as: https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=00adddd65689d995d8bdf306d0850c852ff0fd25 |
Created attachment 1714724 [details] reproducer Description of problem: When compiling the attached program with gcc -fanalyzer -c t.c, I get the warning, which I consider a false-positive, because fclose is called on the caller in the failure case: t.c: In function ‘ini_parse_stream’: t.c:15:12: warning: leak of FILE ‘stream’ [CWE-775] [-Wanalyzer-file-leak] 15 | return 0; | ^ ‘ini_parse’: events 1-6 | | 23 | int ini_parse(const char* filename) | | ^~~~~~~~~ | | | | | (1) entry to ‘ini_parse’ |...... | 28 | file = fopen(filename, "r"); | | ~~~~~~~~~~~~~~~~~~~~ | | | | | (2) opened here | 29 | if (!file) | | ~ | | | | | (3) assuming ‘file’ is non-NULL | | (4) following ‘false’ branch (when ‘file’ is non-NULL)... | 30 | return -1; | 31 | error = ini_parse_file(file); | | ~~~~~~~~~~~~~~~~~~~~ | | | | | (5) ...to here | | (6) calling ‘ini_parse_file’ from ‘ini_parse’ | +--> ‘ini_parse_file’: events 7-8 | | 18 | static int ini_parse_file(FILE* file) | | ^~~~~~~~~~~~~~ | | | | | (7) entry to ‘ini_parse_file’ | 19 | { | 20 | return ini_parse_stream((ini_reader)fgets, file); | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | | | | | (8) calling ‘ini_parse_stream’ from ‘ini_parse_file’ | +--> ‘ini_parse_stream’: events 9-12 | | 9 | static int ini_parse_stream(ini_reader reader, void* stream) | | ^~~~~~~~~~~~~~~~ | | | | | (9) entry to ‘ini_parse_stream’ |...... | 13 | while (reader(line, max_line, stream) != NULL) | | ~ | | | | | (10) following ‘false’ branch... | 14 | ; | 15 | return 0; | | ~ | | | | | (11) ...to here | | (12) ‘stream’ leaks here; was opened at (2) | Version-Release number of selected component (if applicable): gcc-10.2.1-1.fc32.x86_64 How reproducible: always Steps to Reproduce: 1. gcc -fanalyzer -c t.c 2. 3. Actual results: The above warning is shown. Expected results: No warning should be shown. Additional info: It can be worked around by changing ini_parse_stream to taking a FILE pointer rather than a void pointer.