scripts/kernel-doc: match -Werror flag strictly

In our CI testing, we use some commands as below to only turn a specific type of warnings into errors, but we notice that kernel-doc warnings are also turned into errors unexpectedly. $ make KCFLAGS="-Werror=return-type" W=1 kernel/fork.o kernel/fork.c:1406: warning: Function parameter or member 'mm' not described in 'set_mm_exe_file' kernel/fork.c:1406: warning: Function parameter or member 'new_exe_file' not described in 'set_mm_exe_file' kernel/fork.c:1441: warning: Function parameter or member 'mm' not described in 'replace_mm_exe_file' kernel/fork.c:1441: warning: Function parameter or member 'new_exe_file' not described in 'replace_mm_exe_file' kernel/fork.c:1491: warning: Function parameter or member 'mm' not described in 'get_mm_exe_file' kernel/fork.c:1510: warning: Function parameter or member 'task' not described in 'get_task_exe_file' kernel/fork.c:1534: warning: Function parameter or member 'task' not described in 'get_task_mm' kernel/fork.c:2109: warning: bad line: kernel/fork.c:2130: warning: Function parameter or member 'ret' not described in '__pidfd_prepare' kernel/fork.c:2130: warning: Excess function parameter 'pidfd' description in '__pidfd_prepare' kernel/fork.c:2179: warning: Function parameter or member 'ret' not described in 'pidfd_prepare' kernel/fork.c:2179: warning: Excess function parameter 'pidfd' description in 'pidfd_prepare' kernel/fork.c:3195: warning: expecting prototype for clone3(). Prototype was for sys_clone3() instead 13 warnings as Errors make[3]: *** [scripts/Makefile.build:243: kernel/fork.o] Error 13 make[3]: *** Deleting file 'kernel/fork.o' make[2]: *** [scripts/Makefile.build:480: kernel] Error 2 make[1]: *** [/root/linux/Makefile:1913: .] Error 2 make: *** [Makefile:234: __sub-make] Error 2 >From the git history, commit 2c12c8103d8f ("scripts/kernel-doc: optionally treat warnings as errors") introduces a new command-line option to make kernel-doc warnings into errors. It can also read the KCFLAGS environment variable to decide whether to turn this option on, but the regex used for matching may not be accurate enough. It can match both "-Werror" and "-Werror=<diagnostic-type>", so the option is turned on by mistake in the latter case. Fix this by strictly matching the flag "-Werror": there must be a space or start of string in the front, and a space or end of string at the end. This can handle all the following cases correctly: KCFLAGS="-Werror" make W=1 [MATCH] KCFLAGS="-Werror=return-type" make W=1 [NO MATCH] KCFLAGS="-Wcomment -Werror -Wundef" make W=1 [MATCH] KCFLAGS="-Wcomment -Werror=return-type -Wundef" make W=1 [NO MATCH]

YLYujie Liu committed 3 years ago