Re: [PATCH v2 3/4] meson: add support for 'hdr-check'

> Hi Karthik
>
> On 10/04/2025 12:30, Karthik Nayak wrote:
>> The Makefile supports a target called 'hdr-check', which checks if
>> individual header files can be independently compiled. Let's port this
>> functionality to meson, our new build system too. The implementation
>> resembles that of the Makefile and provides the same check.
>
> Thanks for adding this, I've left a few comments below
>
>> Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
>> ---
>>   meson.build | 107 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 107 insertions(+)
>>
>> diff --git a/meson.build b/meson.build
>> index 790d178007..6fce1aa618 100644
>> --- a/meson.build
>> +++ b/meson.build
>> @@ -655,6 +655,12 @@ if git.found()
>>     endforeach
>>   endif
>>
>> +headers_generated = [
>
> To me "generated_headers" would be a more natural name and would match
> the style of "coccinelle_headers" from patch 1 as well as the equivalent
> in the Makefile.
>

>> +  'command-list.h',
>> +  'config-list.h',
>> +  'hook-list.h'
>> +]
>> +
>>   if not get_option('breaking_changes')
>>     builtin_sources += 'builtin/pack-redundant.c'
>>   endif
>> @@ -1995,6 +2001,107 @@ endif
>>
>>   subdir('contrib')
>>
>> +headers_check_exclude = headers_generated
>> +headers_check_exclude += [
>> +  'compat/apple-common-crypto.h',
>> +  'compat/bswap.h',
>> +  'compat/compiler.h',
>> +  'compat/disk.h',
>> +  'compat/fsmonitor/fsm-darwin-gcc.h',
>> +  'compat/fsmonitor/fsm-health.h',
>> +  'compat/fsmonitor/fsm-listen.h',
>> +  'compat/mingw.h',
>> +  'compat/msvc.h',
>> +  'compat/nedmalloc/malloc.c.h',
>> +  'compat/nedmalloc/nedmalloc.h',
>> +  'compat/nonblock.h',
>> +  'compat/obstack.h',
>> +  'compat/poll/poll.h',
>> +  'compat/precompose_utf8.h',
>> +  'compat/regex/regex.h',
>> +  'compat/regex/regex_internal.h',
>> +  'compat/sha1-chunked.h',
>> +  'compat/terminal.h',
>> +  'compat/vcbuild/include/sys/param.h',
>> +  'compat/vcbuild/include/sys/time.h',
>> +  'compat/vcbuild/include/sys/utime.h',
>> +  'compat/vcbuild/include/unistd.h',
>> +  'compat/vcbuild/include/utime.h',
>> +  'compat/win32.h',
>> +  'compat/win32/alloca.h',
>> +  'compat/win32/dirent.h',
>> +  'compat/win32/lazyload.h',
>> +  'compat/win32/path-utils.h',
>> +  'compat/win32/pthread.h',
>> +  'compat/win32/syslog.h',
>> +  'compat/zlib-compat.h',
>> +  't/unit-tests/clar/clar.h',
>> +  't/unit-tests/clar/clar/fixtures.h',
>> +  't/unit-tests/clar/clar/fs.h',
>> +  't/unit-tests/clar/clar/print.h',
>> +  't/unit-tests/clar/clar/sandbox.h',
>> +  't/unit-tests/clar/clar/summary.h',
>> +  't/unit-tests/clar/test/clar_test.h',
>> +  'unicode-width.h',
>> +  'xdiff/xdiff.h',
>> +  'xdiff/xdiffi.h',
>> +  'xdiff/xemit.h',
>> +  'xdiff/xinclude.h',
>> +  'xdiff/xmacros.h',
>> +  'xdiff/xprepare.h',
>> +  'xdiff/xtypes.h',
>> +  'xdiff/xutils.h',
>> +]
>
> Having to manually maintain this list is a bit of a shame as every time
> a new file is added to compat we need to add it to meson.build twice.
> The Makefile avoids this by filtering the list of headers used when
> building git based on their path - can we do the same here?
>

>> +if sha1_backend != 'openssl'
>> +  headers_check_exclude += 'sha1/openssl.h'
>> +endif
>> +if sha256_backend != 'openssl'
>> +  headers_check_exclude += 'sha256/openssl.h'
>> +endif
>> +if sha256_backend != 'nettle'
>> +  headers_check_exclude += 'sha256/nettle.h'
>> +endif
>> +if sha256_backend != 'gcrpyt'
>> +  headers_check_exclude += 'sha256/gcrypt.h'
>> +endif
>> +
>> +if headers.length() != 0 and compiler.get_argument_syntax() == 'gcc'
>> +  hco_targets = []
>> +  foreach h : headers
>> +    if headers_check_exclude.contains(h)
>> +      continue
>> +    endif
>> +
>> +    hcc = custom_target(
>> +      input: h,
>> +      output: h.underscorify() + 'cc',
>> +      command: [
>> +        shell,
>> +        '-c',
>> +        'echo \'#include "git-compat-util.h"\' > @OUTPUT@ && echo -n \'#include "' + h + '"\' >> @OUTPUT@'
>
> This line is rather long. Also do we really need "echo -n" here, the
> Makefile does not use it.
>

>> +      ]
>> +    )
>> +
>> +    hco = custom_target(
>> +      input: hcc,
>> +      output: h.underscorify().replace('.h', '.hco'),
>> +      command: [
>> +        compiler.cmd_array(),
>> +        libgit_c_args,
>> +        '-I', meson.project_source_root(),
>> +        '-I', meson.project_source_root() / 't/unit-tests',
>
> Do you know why we don't need to add these include paths for the
> equivalent rule in the Makefile?
>

>> +        '-o', '/dev/null',
>> +        '-c', '-xc',
>> +        '@INPUT@'
>> +      ]
>> +    )
>> +    hco_targets += hco
>> +  endforeach
>> +
>> +  alias_target('hdr-check', hco_targets)
>> +endif
>> +
>>   foreach key, value : {
>>     'DIFF': diff.full_path(),
>>     'GIT_SOURCE_DIR': meson.project_source_root(),
>>