Re: Build errors when building git on MacOS 11 (x86-64) and for M1 macs

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

[CC-ing the main git@ list for the "bug in git" aspect of this]

On Thu, Jun 10 2021, Nikhil Gupta wrote:

>   | The following shell command exited with status 2:
>   |  
>   | $ CFLAGS=-I/opt/chef-workstation/embedded/include -O3 -D_FORTIFY_SOURCE=2 -fstack-protector CPPFLAGS=-I/opt/chef-workstation/embedded/include -O3
> -D_FORTIFY_SOURCE=2 -fstack-protector CXXFLAGS=-I/opt/chef-workstation/embedded/include -O3 -D_FORTIFY_SOURCE=2 -fstack-protector
> LDFLAGS=-Wl,-rpath,/opt/chef-workstation/embedded/lib -L/opt/chef-workstation/embedded/lib LD_RUN_PATH=/opt/chef-workstation/embedded/lib MAKE=gmake
> OMNIBUS_INSTALL_DIR=/opt/chef-workstation
> PATH=/opt/chef-workstation/bin:/opt/chef-workstation/embedded/bin:/Users/administrator/.buildkite-agent/builds/MM009-local-1/chef/chef-chef-workstation-master-omnibus-adhoc/omnibus/vendor/bundle/ruby/2.7.0/bin:/opt/angry-omnibus-toolchain/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
> PKG_CONFIG_PATH=/opt/chef-workstation/embedded/lib/pkgconfig gmake prefix=/opt/chef-workstation/embedded bindir=/opt/chef-workstation/gitbin -j 10
> [...]
>   | * new script parameters
>   | builtin/archive.c:48:24: error: implicit declaration of function 'archive_format_from_filename' is invalid in C99
> [-Werror,-Wimplicit-function-declaration]
>   | const char *format = archive_format_from_filename(name_hint);
>   | ^
>   | builtin/archive.c:48:24: note: did you mean 'archive_read_open_filename'?
>   | /opt/chef-workstation/embedded/include/archive.h:527:15: note: 'archive_read_open_filename' declared here
>   | __LA_DECL int archive_read_open_filename(struct archive *,
>   | ^
>   | builtin/archive.c:48:15: warning: incompatible integer to pointer conversion initializing 'const char *' with an expression of type 'int'
> [-Wint-conversion]
>   | const char *format = archive_format_from_filename(name_hint);
>   | ^        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   | builtin/archive.c:101:2: error: implicit declaration of function 'init_archivers' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
>   | init_archivers();
>   | ^
>   | builtin/archive.c:111:9: error: implicit declaration of function 'write_archive' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
>   | return write_archive(argc, argv, prefix, the_repository, output, 0);
>   | ^
>   | builtin/archive.c:111:9: note: did you mean 'write_or_die'?
>   | ./cache.h:1737:6: note: 'write_or_die' declared here
>   | void write_or_die(int fd, const void *buf, size_t count);
>   | ^
>   | 1 warning and 3 errors generated.
>   | gmake: *** [Makefile:2431: builtin/archive.o] Error 1
>   | gmake: *** Waiting for unfinished jobs....
>   |  
>   |  

I have no access to such a system, but I think think I see the problem
from what you've supplied here.

You supplied a CFLAGS=-I/opt/chef-workstation/embedded/include which has
an archive.h file that's unrelated to the archive.h file git expects.

Thus we include that and find things unrelated to git, and error when we
encounter a function we expected to have declared in our own archive.h.

The solution is something like defining a config.mak file where you add
flags with BASIC_CFLAGS +=, not =. See config.mak.uname for an
example. You'll then add new directories after our own -I.

This is arguably a bug in git's Makefile in that we should have that
"-I." in an ESSENTIAL_CFLAGS variable or something, I can't think of a
scenario where git would compile without it. That or things in builtin/
should include e.g. ../archive.h, perhaps such a thing isn't portable.

I think (but have not confirmed) that you probably got this far because
your compiler will stick -I. at the /end/ of the flags implicitly (or is
that standardized C behavior? I can't remember).

So it worked until we had a filename conflict, i.e. we'd find strbuf.h
in our own sources, but have an issue with a common name like archive.h.