Check HAVE_CONFIG_H before including "config.h"

[liujisi]

The first step of introducing "config.h"-less BUILD.

[liujisi]

@xfxyjwf for review

[xfxyjwf]

Where is this HAVE_CONFIG_H macro defined?

[liujisi]

It's defined by automake/autoconf I believe. For builds other that the automake, we need to
manually write a config.h and pass -DHAVE_CONFIG_H.

Checked the places where config.h is introduced:

1. to generate pbconfig.h for hash maps/setes, which will be no longer needed.
2. in common.cc for pthread related stuffs. We have macro checks for windows. Thus we need to manually pass -DHAVE_PTHREAD for bazel.
3. gzip streams and tests, which relies on HAVE_ZLIB

[xfxyjwf]

For the config.h, we can:

1. Always generate config.h. This is what we currently do.
2. Do not generate config.h. Instead of generating config.h, the build tools can just pass macros to the compiler directly (e.g., through CXXFLAGS when building with autoconf/automake).
3. Optionally generate config.h. The code can compile both with/without config.h.

I am confused by what you are trying to do in this PR. It seems you are trying to go with option 3). But if the code is required to compile without config.h anyway, why don't we just get rid of the config.h file? (i.e., 2 is strictly better than 3 in my opinion).

[liujisi]

SGTM. The only downside for option 2 is that if in the future we add need more macros from autoconf, passing -DXXX may make the output harder to read.

[liujisi]

Just to capture the discussion we had yesterday.
We will remove config.h includes from srcs, rather than checking HAVE_CONFIG_H:

• Change Makefile.am to pass in HAVR_ZLIB manually
• HAVE_PTHREAD always needs to be set on non-windows platforms, so remove the ifdef on it.

The config.h will still be generated, because

1. otherwise autoconf will pass those macros from -DXXXX in CXXFLAGS, which spams the logs.
2. for users porting the code to other platforms, it is easier to see what macros are potentially needed by looking at the config.h file.

[liujisi]

Removed the includes and fixed cmake as well, PTAL.

[xfxyjwf]

Remove this extra new-line?

[xfxyjwf]

LGTM

You might want to squash the commits into one.

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request) and all commit authors, but as best as we can tell these commits were authored by someone else. If that's the case, please add them to this pull request and have them confirm that they're okay with these commits being contributed to Google. If we're mistaken and you did author these commits, just reply here to confirm.

[googlebot]

CLAs look good, thanks!