misc-include-cleaner false positive

[herbanonymous]

> clang-tidy -checks='*,-llvmlibc-restrict-system-libc-headers,-clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling,-altera-unroll-loops,-concurrency-mt-unsafe,-altera-id-dependent-backward-branch,-readability-function-cognitive-complexity,-*-magic-numbers,-cppcoreguidelines-avoid-non-const-global-variables' vector.c
Error while trying to load a compilation database:
Could not auto-detect compilation database for file "vector.c"
No compilation database found in /u/talib 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.
3771 warnings generated.
/u/talib/vector.c:7:1: warning: included header getopt.h is not used directly [misc-include-cleaner]
    7 | #include <getopt.h>
      | ^~~~~~~~~~~~~~~~~~~
    8 | #include <libgen.h>
/u/talib/vector.c:56:23: warning: no header providing "getopt" is directly included [misc-include-cleaner]
    4 |         while ((opt = getopt(argc, argv, OPTIONS)) != -1) {
      |                       ^
/u/talib/vector.c:59:35: warning: no header providing "optarg" is directly included [misc-include-cleaner]
   59 |                     ifile = fopen(optarg, "re");
      |                                   ^
Suppressed 3768 warnings (3768 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.

[herbanonymous]

using unistd.h instead of getopt.h produces the same result [EDIT: in LLVM version 22.1.2 and Ubuntu LLVM version 18.1.3]

[llvmbot]

@llvm/issue-subscribers-clang-include-cleaner

Author: herbanonymous

Details

[vector.c](https://github.com/user-attachments/files/26546969/vector.c) ``` > clang-tidy -checks='*,-llvmlibc-restrict-system-libc-headers,-clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling,-altera-unroll-loops,-concurrency-mt-unsafe,-altera-id-dependent-backward-branch,-readability-function-cognitive-complexity,-*-magic-numbers,-cppcoreguidelines-avoid-non-const-global-variables' vector.c Error while trying to load a compilation database: Could not auto-detect compilation database for file "vector.c" No compilation database found in /u/talib 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. 3771 warnings generated. /u/talib/vector.c:7:1: warning: included header getopt.h is not used directly [misc-include-cleaner] 7 | #include <getopt.h> | ^~~~~~~~~~~~~~~~~~~ 8 | #include <libgen.h> /u/talib/vector.c:56:23: warning: no header providing "getopt" is directly included [misc-include-cleaner] 4 | while ((opt = getopt(argc, argv, OPTIONS)) != -1) { | ^ /u/talib/vector.c:59:35: warning: no header providing "optarg" is directly included [misc-include-cleaner] 59 | ifile = fopen(optarg, "re"); | ^ Suppressed 3768 warnings (3768 in non-user code). Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well. ```

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: herbanonymous

Details

[vector.c](https://github.com/user-attachments/files/26546969/vector.c) ``` > clang-tidy -checks='*,-llvmlibc-restrict-system-libc-headers,-clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling,-altera-unroll-loops,-concurrency-mt-unsafe,-altera-id-dependent-backward-branch,-readability-function-cognitive-complexity,-*-magic-numbers,-cppcoreguidelines-avoid-non-const-global-variables' vector.c Error while trying to load a compilation database: Could not auto-detect compilation database for file "vector.c" No compilation database found in /u/talib 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. 3771 warnings generated. /u/talib/vector.c:7:1: warning: included header getopt.h is not used directly [misc-include-cleaner] 7 | #include <getopt.h> | ^~~~~~~~~~~~~~~~~~~ 8 | #include <libgen.h> /u/talib/vector.c:56:23: warning: no header providing "getopt" is directly included [misc-include-cleaner] 4 | while ((opt = getopt(argc, argv, OPTIONS)) != -1) { | ^ /u/talib/vector.c:59:35: warning: no header providing "optarg" is directly included [misc-include-cleaner] 59 | ifile = fopen(optarg, "re"); | ^ Suppressed 3768 warnings (3768 in non-user code). Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well. ```

[AaronBallman]

Confirmed-ish: https://godbolt.org/z/bGvr7coPz

Looking at the -E output, it seems that the symbol comes from a details header:

# 91 "/usr/include/x86_64-linux-gnu/bits/getopt_core.h" 3 4
extern int getopt (int ___argc, char *const *___argv, const char *__shortopts)
       __attribute__ ((__nothrow__ )) __attribute__ ((__nonnull__ (2, 3)));

which may explain why misc-include-cleaner is reporting the false positive. It's sort of a true positive, but we don't want to encourage users to include the detail header instead, I suspect.