Re: [PATCH] New "make check-headers" rule.

[Pedro Alves <palves@redhat.com>]

On 11/14/2013 09:21 PM, Tom Tromey wrote:
>>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:
> 
> Pedro> New "make check-headers" rule.
> 
> It seems like a good idea to me.
> 
> Pedro> +check-headers:
> Pedro> +	@echo Checking headers.
> Pedro> +	for i in $(CHECK_HEADERS) ; do \
> Pedro> +		$(NODEPS_COMPILE) -Wno-error $(PYTHON_CFLAGS) -include defs.h \
> Pedro> +			$(srcdir)/$$i -o /dev/null ; \
> Pedro> +	done
> 
> I'm curious why -Wno-error.

No good reason, I'm afraid.

> Also why not -fsyntax-only?

It hadn't crossed my radar.  

Looking at it, I wasn't sure it was the exact same -- e.g.,
whether it expanded C++ templates, but google convinced me it
does.  I looked over gcc's codebase (grep for flag_syntax_only)
and I saw things like folding and optimization possibly behaving
differently when that flag in enabled.  I was going to prefer
not using the flag on those grounds, but then I timed it:

make check-headers w/ -o /dev/null

 real    1m35.383s
 user    0m44.862s
 sys     0m8.140s

make check-headers w/ -fsyntax-only:

 real    0m42.648s
 user    0m32.563s
 sys     0m7.891s

That's a considerable difference, so that convinced me.
Nice one.

If that flag indeed causes a difference of visible
behavior wrt to errors detected, I guess I'll call it
a gcc bug.

One extra thing we discussed offline is that with
-fsyntax-only, gcc needs to be told the language being
compiled explicitly ("-x c"), otherwise we get:

$ gcc -c -fsyntax-only (...)
cc1: error: output filename specified twice

Below's what I pushed.

Thanks.

----------
New "make check-headers" rule.

Tries to compile each header in isolation, thus ensuring headers are
self-contained.

Defaults to checking all $HFILES_NO_SRCDIR headers.

Do:

  make check-headers CHECK_HEADERS="header.h list.h"

to check specific headers.

gdb/
2014-01-13  Pedro Alves  <palves@redhat.com>

        * Makefile.in (CHECK_HEADERS): New variable.
        (check-headers:): New rule.
---
 gdb/ChangeLog   |  5 +++++
 gdb/Makefile.in | 22 ++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 6cdafcc..18ed4d3 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2014-01-13  Pedro Alves  <palves@redhat.com>
+
+        * Makefile.in (CHECK_HEADERS): New variable.
+        (check-headers:): New rule.
+
 2014-01-13  Tom Tromey  <tromey@redhat.com>
 
 	* cli/cli-setshow.c (do_set_command): Update.
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 824b26b..9811cbe 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -1050,6 +1050,28 @@ check//%: force
 	    "$$target"; \
 	else true; fi
 
+# The set of headers checked by 'check-headers' by default.
+CHECK_HEADERS = $(HFILES_NO_SRCDIR)
+
+# Try to compile each header in isolation, thus ensuring headers are
+# self-contained.
+#
+# Defaults to checking all $HFILES_NO_SRCDIR headers.
+#
+# Do:
+#
+#    make check-headers CHECK_HEADERS="header.h list.h"
+#
+# to check specific headers.
+#
+check-headers:
+	@echo Checking headers.
+	for i in $(CHECK_HEADERS) ; do \
+		$(CC) -x c -c -fsyntax-only $(INTERNAL_CFLAGS) \
+			-include defs.h $(srcdir)/$$i ; \
+	done
+.PHONY: check-headers
+
 info install-info clean-info dvi pdf install-pdf html install-html: force
 	@$(MAKE) $(FLAGS_TO_PASS) DO=$@ "DODIRS=$(SUBDIRS)" subdir_do
 
-- 
1.7.11.7