[ccache] ccache has issues with current Apple compilers

[Tom Lane]

I tried to install ccache 3.1.9 on a current Mac system (OS X 10.9.3,
Xcode 5.1.1).  Configure and compile went cleanly, with the exception
of two probably-harmless warnings:

manifest.c:223:2: warning: shift count >= width of type [-Wshift-count-overflow]
        READ_INT(1, version);
        ^~~~~~~~~~~~~~~~~~~~
manifest.c:150:10: note: expanded from macro 'READ_INT'
                        (var) <<= 8; \
                              ^   ~
manifest.c:230:2: warning: shift count >= width of type [-Wshift-count-overflow]
        READ_INT(1, mf->hash_size);
        ^~~~~~~~~~~~~~~~~~~~~~~~~~
manifest.c:150:10: note: expanded from macro 'READ_INT'
                        (var) <<= 8; \
                              ^   ~
2 warnings generated.

I made this change to silence that, since I think that the C standard
allows compilers to consider the case undefined behavior:

$ diff -c manifest.c~ manifest.c
*** manifest.c~ Sun Jan  6 11:57:59 2013
--- manifest.c  Sat May 31 13:42:53 2014
***************
*** 147,154 ****
                        if (ch_ == EOF) { \
                                goto error; \
                        } \
!                       (var) <<= 8; \
!                       (var) |= ch_ & 0xFF; \
                } \
        } while (0)
  
--- 147,153 ----
                        if (ch_ == EOF) { \
                                goto error; \
                        } \
!                       (var) = (((unsigned int) (var)) << 8) | (ch_ & 0xFF); \
                } \
        } while (0)
  
but it's probably not really an issue.  However, "make test" refuses
to do anything much:

...
PASSED: 178 assertions, 64 tests, 9 suites
CC='gcc' ./test.sh
WARNING: Compiler gcc not supported (version: Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/c++/4.2.1) -- not running tests

I looked at test.sh and concluded that it simply didn't recognize the
output of "gcc --version", which looks like this:

$ gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/c++/4.2.1
Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn)
Target: x86_64-apple-darwin13.2.0
Thread model: posix

So I diked out that check from the test script and tried again.
The first half dozen test suites went OK, but in the "basedir"
testsuite I got a lot of chatter:

clang: warning: argument unused during compilation: '-I /Users/tgl/src/ccache-3.1.9/testdir.20963/dir1/include'
clang: warning: argument unused during compilation: '-I /Users/tgl/src/ccache-3.1.9/testdir.20963/dir2/include'
clang: warning: argument unused during compilation: '-I include'
clang: warning: argument unused during compilation: '-I include'
clang: warning: argument unused during compilation: '-I include'
[ much more in the same vein... ]

and then the "pch" testsuite failed altogether:

starting testsuite pch
SUITE: "pch", TEST: "no -fpch-preprocess, -include" - Expected "cache miss" to be 1, got 0
cache directory                     /Users/tgl/src/ccache-3.1.9/testdir.20963/.ccache
cache hit (direct)                     0
cache hit (preprocessed)               0
cache miss                             0
preprocessor error                     1
files in cache                         0
cache size                             0 Kbytes
max cache size                       1.0 Gbytes
TEST FAILED
Test data and log file have been left in testdir.20963
make: *** [test] Error 1

I did some further experiments and concluded that ccache is in fact kind
of broken: when I try to compile a large project with it, I get thousands
of weird warnings that do not appear when using gcc directly (many of them
the same kind of "unused -I argument" bleat shown above, but others are
warnings about C constructs that I don't normally see any warnings about).
The resulting executables seem to work, but I can't use a toolchain that's
this noisy.  In any case, surely it's unexpected that ccache would change
the compiler's warning behavior?

I don't know enough about ccache to debug this, but will be happy
to supply further info if given directions how to get it.

(BTW, I successfully installed the same ccache source code on two
older Apple systems, and it's working as expected there.)

			regards, tom lane