[PATCH] Makefile: add option to disable automatic dependency generation
- From
Jonathan Nieder <jrnieder@gmail.com>
- Date
- Nov 18, 2011, 04:57 UTC
- Message-ID
- <20111118045742.GA25145@elie.hsd1.il.comcast.net>
- In-Reply-To
- <CACsJy8A44PFtYrm8NQU+48sVkOe8mjJyO9opO5-TwRtAd-TKsQ@mail.gmail.com>
Duy noticed that now that the COMPUTE_HEADER_DEPENDENCIES feature is turned on automatically for compilers that support it (see v1.7.8-rc0~142^2~1, 2011-08-18), there is no easy way to force it off. For example, setting COMPUTE_HEADER_DEPENDENCIES to the empty string in config.mak just tells the makefile to treat it as undefined and run a test command to see if the -MMD option is supported.
Introduce a new NO_COMPUTE_HEADER_DEPENDENCIES variable that forces the feature off. The new semantics:
- If NO_COMPUTE_HEADER_DEPENDENCIES is set to a nonempty string, the -MMD option will not be used. The build relies on hard-coded dependencies in the "ifndef USE_COMPUTED_HEADER_DEPENDENCIES" section of the Makefile instead.
- If COMPUTE_HEADER_DEPENDENCIES is empty and NO_COMPUTE_... is nonempty, the build uses gcc's on-the-fly dependency generation feature.
- If neither is nonempty, the makefile runs a quick test command to decide whether the compiler supports the -MMD option and whether to enable this feature.
Inspired-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> --- Nguyen Thai Ngoc Duy wrote:
> Hmm.. I guess it's my compiler's fault then. Next question, how can I > disable this feature?
"make COMPUTE_HEADER_DEPENDENCIES=" works. But there's no way aside from "override COMPUTE_HEADER_DEPENDENCIES=" to do that in config.mak. And yuck.
By the way, I'm not convinced it's your compiler's fault. It might be my compiler's fault. More reading to do...
Makefile | 15 ++++++++++++++- 1 files changed, 14 insertions(+), 1 deletions(-)
diff --git a/Makefile b/Makefile index ee34eab8..e4a658f6 100644 --- a/Makefile +++ b/Makefile @@ -250,6 +250,13 @@ all:: # DEFAULT_EDITOR='$GIT_FALLBACK_EDITOR', # DEFAULT_EDITOR='"C:\Program Files\Vim\gvim.exe" --nofork' # +# Define COMPUTE_HEADER_DEPENDENCIES if your compiler supports the -MMD option +# and you want to avoid rebuilding objects when an unrelated header file +# changes. +# +# Define NO_COMPUTE_HEADER_DEPENDENCIES if you want to disable automatic +# dependency generation even though your compiler is detected to support it. +# # Define CHECK_HEADER_DEPENDENCIES to check for problems in the hard-coded # dependency rules. # @@ -1245,10 +1252,16 @@ endif endif ifdef CHECK_HEADER_DEPENDENCIES +NO_COMPUTE_HEADER_DEPENDENCIES = YesPlease +endif + +ifdef NO_COMPUTE_HEADER_DEPENDENCIES COMPUTE_HEADER_DEPENDENCIES = USE_COMPUTED_HEADER_DEPENDENCIES = -else +endif + ifndef COMPUTE_HEADER_DEPENDENCIES +ifndef NO_COMPUTE_HEADER_DEPENDENCIES dep_check = $(shell $(CC) $(ALL_CFLAGS) \ -c -MF /dev/null -MMD -MP -x c /dev/null -o /dev/null 2>&1; \ echo $$?)
-- 1.7.8.rc2