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

On Thu, Jun 10, 2021 at 10:36:27AM -0400, Jeff King wrote:

Most compilers put the directory of the source file at the start of the
search path. E.g., gcc says under -I:

  1. For the quote form of the include directive, the directory of the
     current file is searched first.

Which is why we need "-I." at all; we are finding "archive.h" from
"builtin/*.c". I'm not sure what "current file" there means, or how
portable it is. Is it the source file being filed, or the file
containing the #include directive?

I'd hope it's consistently the latter. Otherwise "foo.h" which includes
"bar.h" cannot be included as "../foo.h" (from builtin/foo.c) and as
"foo.h" (from top-level foo.c).

If so, then yeah, using "../archive.h" (and dropping -I. entirely) would
be an option. Which is nice, because it makes things less magical and
more predictable (think what confusion we'd see if we introduced
"archive.h" into builtin/ ourselves).

There's a related case, which is that within trace2/foo.c, we'd include
trace2/foo.h. Without "-I.", the correct include there is just "foo.h".

So what was explicit actually becomes implicit. Here's a real example to
make this file work without -I:

  diff --git a/trace2/tr2_tgt_perf.c b/trace2/tr2_tgt_perf.c
  index a8018f18cc..592c194ab4 100644
  --- a/trace2/tr2_tgt_perf.c
  +++ b/trace2/tr2_tgt_perf.c
  @@ -1,15 +1,15 @@
  -#include "cache.h"
  -#include "config.h"
  -#include "run-command.h"
  -#include "quote.h"
  -#include "version.h"
  -#include "json-writer.h"
  -#include "trace2/tr2_dst.h"
  -#include "trace2/tr2_sid.h"
  -#include "trace2/tr2_sysenv.h"
  -#include "trace2/tr2_tbuf.h"
  -#include "trace2/tr2_tgt.h"
  -#include "trace2/tr2_tls.h"
  +#include "../cache.h"
  +#include "../config.h"
  +#include "../run-command.h"
  +#include "../quote.h"
  +#include "../version.h"
  +#include "../json-writer.h"
  +#include "tr2_dst.h"
  +#include "tr2_sid.h"
  +#include "tr2_sysenv.h"
  +#include "tr2_tbuf.h"
  +#include "tr2_tgt.h"
  +#include "tr2_tls.h"

So I dunno. I had hoped it would be a strict readability improvement,
but now I'm not so sure.

-Peff