Re: [PATCH v2 08/12] mingw: rely on MSYS2's metadata instead of hard-coding it

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Hannes,

On Sat, 15 Aug 2026, Johannes Sixt wrote:

> Am 12.08.26 um 09:52 schrieb Johannes Schindelin via GitGitGadget:
> > diff --git a/config.mak.uname b/config.mak.uname
> > index 21f53e3f7e..3a90995587 100644
> > --- a/config.mak.uname
> > +++ b/config.mak.uname
> > @@ -465,14 +465,8 @@ ifeq ($(uname_S),Windows)
> >  	GIT_VERSION := $(GIT_VERSION).MSVC
> >  	pathsep = ;
> >  	# Assume that this is built in Git for Windows' SDK
> > -        ifeq (MINGW32,$(MSYSTEM))
> > -		prefix = /mingw32
> > -        else
> > -                ifeq (CLANGARM64,$(MSYSTEM))
> > -			prefix = /clangarm64
> > -                else
> > -			prefix = /mingw64
> > -                endif
> > +        ifneq (,$(MSYSTEM))
> > +		prefix = $(MINGW_PREFIX)
> >          endif
> >  	# Prepend MSVC 64-bit tool-chain to PATH.
> >  	#
> > @@ -755,6 +749,10 @@ ifeq ($(uname_S),MINGW)
> >  		BASIC_LDFLAGS += -Wl,--dynamicbase
> >          endif
> >          ifneq (,$(MSYSTEM))
> > +                ifeq ($(MINGW_PREFIX),$(filter-out /%,$(MINGW_PREFIX)))
> > +			# Override if empty or does not start with a slash
> > +			MINGW_PREFIX := /$(shell echo '$(MSYSTEM)' | tr A-Z a-z)
> > +                endif
> >  		prefix = $(MINGW_PREFIX)
> >  		HOST_CPU = $(patsubst %-w64-mingw32,%,$(MINGW_CHOST))
> >  		BASIC_LDFLAGS += -Wl,--pic-executable
> 
> At this point, MINGW_PREFIX is only used to set prefix.
> 
> Only in 12/12 is the variable (and ENSURE_MSYSTEM_IS_SET) used to drive
> C code. Therefore, it seems that the following hunks concerning the
> CMake and meson build systems do not belong in this patch, yet, but only
> in 12/12.

Ah, right, the following hunks do touch the ENSURE_MSYSTEM_IS_SET stuff.
But they _also_ add the `MINGW_PREFIX` stuff.

Will disentangle.

Ciao,
Johannes

> 
> > diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
> > index a57c4b464f..7285bd9ac2 100644
> > --- a/contrib/buildsystems/CMakeLists.txt
> > +++ b/contrib/buildsystems/CMakeLists.txt
> > @@ -256,7 +256,14 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
> >  				_CONSOLE DETECT_MSYS_TTY STRIP_EXTENSION=".exe"  NO_SYMLINK_HEAD UNRELIABLE_FSTAT
> >  				NOGDI OBJECT_CREATION_MODE=1 __USE_MINGW_ANSI_STDIO=0
> >  				OVERRIDE_STRDUP MMAP_PREVENTS_DELETE USE_WIN32_MMAP
> > -				HAVE_WPGMPTR ENSURE_MSYSTEM_IS_SET HAVE_RTLGENRANDOM)
> > +				HAVE_WPGMPTR HAVE_RTLGENRANDOM)
> > +	if(CMAKE_GENERATOR_PLATFORM STREQUAL "x64")
> > +		add_compile_definitions(ENSURE_MSYSTEM_IS_SET="MINGW64" MINGW_PREFIX="mingw64")
> > +	elseif(CMAKE_GENERATOR_PLATFORM STREQUAL "arm64")
> > +		add_compile_definitions(ENSURE_MSYSTEM_IS_SET="CLANGARM64" MINGW_PREFIX="clangarm64")
> > +	elseif(CMAKE_GENERATOR_PLATFORM STREQUAL "x86")
> > +		add_compile_definitions(ENSURE_MSYSTEM_IS_SET="MINGW32" MINGW_PREFIX="mingw32")
> > +	endif()
> >  	list(APPEND compat_SOURCES
> >  		compat/mingw.c
> >  		compat/winansi.c
> > diff --git a/meson.build b/meson.build
> > index 7073d5844d..a8aba81e29 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -1318,7 +1318,6 @@ elif host_machine.system() == 'windows'
> >  
> >    libgit_c_args += [
> >      '-DDETECT_MSYS_TTY',
> > -    '-DENSURE_MSYSTEM_IS_SET',
> >      '-DNATIVE_CRLF',
> >      '-DNOGDI',
> >      '-DNO_POSIX_GOODIES',
> > @@ -1328,6 +1327,20 @@ elif host_machine.system() == 'windows'
> >      '-D__USE_MINGW_ANSI_STDIO=0',
> >    ]
> >  
> > +  msystem = get_option('msystem')
> > +  if msystem != ''
> > +    mingw_prefix = get_option('mingw_prefix')
> > +    if mingw_prefix == ''
> > +      mingw_prefix = msystem.to_lower()
> > +    elif mingw_prefix.startswith('/')
> > +      mingw_prefix = mingw_prefix.substring(1)
> > +    endif
> > +    libgit_c_args += [
> > +      '-DENSURE_MSYSTEM_IS_SET="' + msystem + '"',
> > +      '-DMINGW_PREFIX="' + mingw_prefix + '"'
> > +    ]
> > +  endif
> > +
> >    libgit_dependencies += compiler.find_library('ntdll')
> >    libgit_include_directories += 'compat/win32'
> >    if compiler.get_id() == 'msvc'
> > diff --git a/meson_options.txt b/meson_options.txt
> > index dc88f130d7..becf4689bf 100644
> > --- a/meson_options.txt
> > +++ b/meson_options.txt
> > @@ -21,6 +21,10 @@ option('runtime_prefix', type: 'boolean', value: false,
> >    description: 'Resolve ancillary tooling and support files relative to the location of the runtime binary instead of hard-coding them into the binary.')
> >  option('sane_tool_path', type: 'array', value: [],
> >    description: 'An array of paths to pick up tools from in case the normal tools are broken or lacking.')
> > +option('msystem', type: 'string', value: '',
> > +  description: 'Fall-back on Windows when MSYSTEM is not set.')
> > +option('mingw_prefix', type: 'string', value: '',
> > +  description: 'Fall-back on Windows when MINGW_PREFIX is not set.')
> >  
> >  # Build information compiled into Git and other parts like documentation.
> >  option('build_date', type: 'string', value: '',
> 
> -- Hannes
> 
>