clang-tidy fails bugprone check - llvm

Question

I'm experimenting with clang-tidy using the following file:
#include <stdio.h>
int main(int argc, char **argv)
{
int i=2; int j=1;
if (argc = 5) { return 2; }
while (i<argc) { j++; }
return 0;
}
I aim to detect the infinite loop with:
$ clang-tidy -checks=bugprone-infinite-loop main.c
but all that clang-tidy finds is the = instead of == thing:
Error while trying to load a compilation database:
Could not auto-detect compilation database for file "main.c"
No compilation database found in /home/oren or any parent directory
fixed-compilation-database: Error while opening fixed database: No such file or directory
json-compilation-database: Error while opening JSON database: No such file or directory
Running without flags.
1 warning generated.
/home/oren/main.c:6:11: warning: using the result of an assignment as a condition without parentheses [clang-diagnostic-parentheses]
if (argc = 5) { return 2; }
~~~~ ^ ~
( == )
/home/oren/main.c:6:11: note: place parentheses around the assignment to silence this warning
/home/oren/main.c:6:11: note: use '==' to turn this assignment into an equality comparison

Answer 1

You are using a feature from a yet unreleased version of LLVM (10.0.0).
On my system (windows) your file works as expected:
>clang-tidy10 -checks=bugprone-infinite-loop infloop.c --
1 warning generated.
\infloop.c:6:5: warning: this loop is infinite; none of its con
dition variables (i, argc) are updated in the loop body [bugprone-infinite-loop]
while (i<argc) { j++; }
^
The only modification I did on the file is removing the unecessary #include. I also added -- (double dash) to the command to get rid of missing compilation database errors. I am using a prebuilt binary from https://llvm.org/builds/
My best guess here is that you are using an older build of clang-tidy where this is not detected. For reference my version is 10.0.0-e20a1e486e1, you can see yours by running:
>clang-tidy --version
I'd also check if you are actually running the check(s) you are expected to run via:
$ clang-tidy -checks=bugprone-infinite-loop main.c --list-checks
P.S. The warning message you got at first was clang-diagnostic based, this has nothing to do with clang-tidy but rather with clang compilation