meson: add support for 'hdr-check'

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.

Since meson builds are out-of-tree, header dependencies are not
automatically met. So unlike the Makefile version, we also need to add
the required dependencies.

Also add the 'xdiff/' dir to the list of 'third_party_sources' as those
headers must be skipped from the checks too. This also skips the folder
from the 'coccinelle' checks, this is okay, since this code is an
external dependency.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/meson.build b/meson.build
index 4618804c7a19b1e0908de34ce56b68aff5d3131c..22fc65ec80ba6a840186a53393bce8663c26e2ab 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -645,6 +645,7 @@ third_party_excludes = [
   ':!sha1dc',
   ':!t/unit-tests/clar',
   ':!t/t[0-9][0-9][0-9][0-9]*',
+  ':!xdiff',
 ]
 
 headers_to_check = []
@@ -1994,6 +1995,68 @@ endif
 
 subdir('contrib')
 
+exclude_from_check_headers = [
+  'compat/',
+  'unicode-width.h',
+]
+
+if sha1_backend != 'openssl'
+  exclude_from_check_headers += 'sha1/openssl.h'
+endif
+if sha256_backend != 'openssl'
+  exclude_from_check_headers += 'sha256/openssl.h'
+endif
+if sha256_backend != 'nettle'
+  exclude_from_check_headers += 'sha256/nettle.h'
+endif
+if sha256_backend != 'gcrypt'
+  exclude_from_check_headers += 'sha256/gcrypt.h'
+endif
+
+if headers_to_check.length() != 0 and compiler.get_argument_syntax() == 'gcc'
+  hco_targets = []
+  foreach h : headers_to_check
+    skip_header = false
+    foreach exclude : exclude_from_check_headers
+      if h.startswith(exclude)
+        skip_header = true
+        break
+      endif
+    endforeach
+
+    if skip_header
+      continue
+    endif
+
+    hcc = custom_target(
+      input: h,
+      output: h.underscorify() + 'cc',
+      command: [
+        shell,
+        '-c',
+        'echo \'#include "git-compat-util.h"\' > @OUTPUT@ && echo \'#include "' + h + '"\' >> @OUTPUT@'
+      ]
+    )
+
+    hco = custom_target(
+      input: hcc,
+      output: fs.replace_suffix(h.underscorify(), '.hco'),
+      command: [
+        compiler.cmd_array(),
+        libgit_c_args,
+        '-I', meson.project_source_root(),
+        '-I', meson.project_source_root() / 't/unit-tests',
+        '-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(),