[PATCH] Avoid running $(CXX) during build to obtain header file paths
Carlos O'Donell
carlos@redhat.com
Tue Sep 20 19:21:00 GMT 2016
On 09/20/2016 07:19 AM, Florian Weimer wrote:
> On my machine, this cuts down no-op rebuild time from about 10 seconds to around 8.5 seconds.
>
> (If you change the compiler, you better re-run configure anyway.)
This looks good to me.
I agree that if you change the compiler, there are a lot of niggling
details that need to be updated and re-running configure is the only
safe way we support that (particularly given that glibc manually links
several things together using implementation dependent knowledge).
Computing this early and once seems like a very reasonable optimization.
> Avoid running $(CXX) during build to obtain header file paths
>
> This reduces the build time somewhat and is particularly noticeable
> during rebuilds with few code changes.
>
> 2016-09-20 Florian Weimer <fweimer@redhat.com>
>
> Avoid running $(CXX) during build to obtain header file paths.
> * configure.ac (CXX_SYSINCLUDES, CXX_CMATH_HEADER): Set.
> * config.make.in (c++-cstdlib-header, c++-cmath-header): Define.
> * Makerules (cstdlib, cmath): Remove variables. Use
> $(c++-cstdlib-header), $(c++-cmath-header) instead.
> * configure: Regenerate.
>
> diff --git a/Makerules b/Makerules
> index 748790b..e865782 100644
> --- a/Makerules
> +++ b/Makerules
> @@ -121,14 +121,10 @@ ifneq (,$(CXX))
> # will be used instead of /usr/include/stdlib.h and /usr/include/math.h.
> before-compile := $(common-objpfx)cstdlib $(common-objpfx)cmath \
> $(before-compile)
> -cstdlib=$(shell echo "\#include <cstdlib>" | $(CXX) -M -MP -x c++ - \
> - | sed -n "/cstdlib:/{s/:$$//;p}")
> -$(common-objpfx)cstdlib: $(cstdlib)
> +$(common-objpfx)cstdlib: $(c++-cstdlib-header)
> $(INSTALL_DATA) $< $@T
> $(move-if-change) $@T $@
> -cmath=$(shell echo "\#include <cmath>" | $(CXX) -M -MP -x c++ - \
> - | sed -n "/cmath:/{s/:$$//;p}")
> -$(common-objpfx)cmath: $(cmath)
> +$(common-objpfx)cmath: $(c++-cmath-header)
> $(INSTALL_DATA) $< $@T
> $(move-if-change) $@T $@
> endif
> diff --git a/config.make.in b/config.make.in
> index 95c6f36..04a8b3e 100644
> --- a/config.make.in
> +++ b/config.make.in
> @@ -45,6 +45,8 @@ defines = @DEFINES@
> sysheaders = @sysheaders@
> sysincludes = @SYSINCLUDES@
> c++-sysincludes = @CXX_SYSINCLUDES@
> +c++-cstdlib-header = @CXX_CSTDLIB_HEADER@
> +c++-cmath-header = @CXX_CMATH_HEADER@
> all-warnings = @all_warnings@
> enable-werror = @enable_werror@
>
> diff --git a/configure b/configure
> index 17625e1..6ff2527 100755
> --- a/configure
> +++ b/configure
> @@ -635,6 +635,8 @@ BISON
> INSTALL_INFO
> PERL
> BASH_SHELL
> +CXX_CMATH_HEADER
> +CXX_CSTDLIB_HEADER
> CXX_SYSINCLUDES
> SYSINCLUDES
> AUTOCONF
> @@ -5054,6 +5056,18 @@ fi
>
>
>
> +# Obtain some C++ header file paths. This is used to make a local
> +# copy of those headers in Makerules.
> +if test -n "$CXX"; then
> + find_cxx_header () {
> + echo "#include <$1>" | $CXX -M -MP -x c++ - | sed -n "/$1:/{s/:\$//;p}"
> + }
> + CXX_CSTDLIB_HEADER="$(find_cxx_header cstdlib)"
> + CXX_CMATH_HEADER="$(find_cxx_header cmath)"
> +fi
> +
> +
> +
> # Test if LD_LIBRARY_PATH contains the notation for the current directory
> # since this would lead to problems installing/building glibc.
> # LD_LIBRARY_PATH contains the current directory if one of the following
> diff --git a/configure.ac b/configure.ac
> index 33bcd62..9938ab0 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -1039,6 +1039,18 @@ fi
> AC_SUBST(SYSINCLUDES)
> AC_SUBST(CXX_SYSINCLUDES)
>
> +# Obtain some C++ header file paths. This is used to make a local
> +# copy of those headers in Makerules.
> +if test -n "$CXX"; then
> + find_cxx_header () {
> + echo "#include <$1>" | $CXX -M -MP -x c++ - | sed -n "/$1:/{s/:\$//;p}"
> + }
> + CXX_CSTDLIB_HEADER="$(find_cxx_header cstdlib)"
> + CXX_CMATH_HEADER="$(find_cxx_header cmath)"
> +fi
> +AC_SUBST(CXX_CSTDLIB_HEADER)
> +AC_SUBST(CXX_CMATH_HEADER)
> +
> # Test if LD_LIBRARY_PATH contains the notation for the current directory
> # since this would lead to problems installing/building glibc.
> # LD_LIBRARY_PATH contains the current directory if one of the following
--
Cheers,
Carlos.
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