Hi all: I have this cross-compiling Autoconf project: https://github.com/rdiez/JtagDue/tree/master/Project I am not using Autoconf for portability, but mainly for handling C/C++ dependencies, so that not everything is rebuilt when I change one source file. This is just an example project, I have others that are bigger, and I rebuild many of them automatically overnight. That is why I am looking at speeding up the configuration process. The example project above does the following checks: checking for a BSD-compatible install... /usr/bin/install -c checking whether build environment is sane... yes checking for arm-none-eabi-strip... arm-none-eabi-strip checking for a race-free mkdir -p... /bin/mkdir -p checking for gawk... gawk checking whether make sets $(MAKE)... yes checking whether make supports nested variables... yes checking whether make supports nested variables... (cached) yes checking for arm-none-eabi-gcc... ccache arm-none-eabi-gcc checking whether we are cross compiling... yes checking for suffix of object files... o checking whether the compiler supports GNU C... yes checking whether ccache arm-none-eabi-gcc accepts -g... yes checking for ccache arm-none-eabi-gcc option to enable C11 features... none needed checking whether ccache arm-none-eabi-gcc understands -c and -o together... yes checking whether make supports the include directive... yes (GNU style) checking dependency style of ccache arm-none-eabi-gcc... gcc3 checking whether the compiler supports GNU C++... yes checking whether ccache arm-none-eabi-g++ accepts -g... yes checking for ccache arm-none-eabi-g++ option to enable C++11 features... none needed checking dependency style of ccache arm-none-eabi-g++... gcc3 checking dependency style of ccache arm-none-eabi-gcc... gcc3 checking for arm-none-eabi-ranlib... arm-none-eabi-gcc-ranlib Is there a way to speed these checks up? The platform is always a reasonably modern Linux, the compiler is always GCC, and ccache is always at least version 3.7.7, so most checks are unnecessary (for me). Things I can think of: - 'install' can be assumed to be OK. - 'mkdir' can be assumed to be OK. - I am always using GNU Make, so all 3 checks around make are dispensable. - I am always using GCC, so checking whether it accepts -g etc. is not necessary. Is there any article or blog post somewhere with speed-up hints for Autoconf? I am aware that Autoconf has an optional config cache, but this time I am specifically looking for other ways. One of the problems of the config cache is that I cannot share a config.cache for all possible build types of one project, let alone different projects. What I mean is that, if I configure the project above in different out-of-tree subdirectories (one for an ARM target as a debug build, another one for an Intel target as a release build, etc.), then I cannot easily share a global configure.cache with only the result of global checks like "whether mkdir -p" is race free. Even if I managed to share one config.cache, I am not sure that multiple projects building in parallel would not corrupt it (race condition). That is not documented as far as I can tell. I could try to generate a fake cache file, but that is not straightforward, and it is always somewhat brittle. For example, you cannot easily guarantee that the pre-calculated cache entries are actually being used by the next Autoconf version. Thanks in advance, rdiez
