[PATCH] builtin/index-pack.c: Fix some pthread_t misuse

On cygwin, sparse complains as follows:

        SP builtin/index-pack.c
    builtin/index-pack.c:892:49: warning: Using plain integer as \
        NULL pointer

The warning refers to code which assigns zero to a pthread_t thread handle. In this case, the pthread_t handle type is a pointer type, which results in the above warning. On Linux a pthread_t is defined as an integer type (unsigned long int for me) and so sparse does not issue any such warning.

However, pthread_t is intended to be an opaque (implementation defined) type. For example, an implementation may choose to use a structure to implement the type. Therefore, assigning zero (or any other constant) to a pthread_t is not supported in general.

As a case in point, the pthread emulation code on MinGW defines the pthread_t type using a structure (see compat/win32/pthread.h:57), which results in gcc complaining as follows:

        CC builtin/index-pack.o
    builtin/index-pack.c: In function 'get_thread_data':
    builtin/index-pack.c:290: error: invalid operands to binary == \
        (have 'pthread_t' and 'pthread_t')
    builtin/index-pack.c: In function 'resolve_one_delta':
    builtin/index-pack.c:302: error: invalid operands to binary == \
        (have 'pthread_t' and 'pthread_t')
    builtin/index-pack.c: In function 'parse_pack_objects':
    builtin/index-pack.c:892: error: incompatible types when assigning \
        to type 'pthread_t' from type 'int'
    make: *** [builtin/index-pack.o] Error 1

Note that, for the same reason given above, you can not, in general, directly compare pthread_t handles with the built-in equality operator. In order to compare pthread_t's for equality, the POSIX standard requires the use of pthread_equal().

In order to fix the warnings and errors, we replace the use of the '==' operator with corresponding calls to pthread_equal() and remove the statement which assigns zero to the thread handle.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
---

Hi Nguyen,

commit ee66dabd ("index-pack: support multithreaded delta resolving", 02-03-2012) causes a build failure on MinGW. This patch makes a small improvement - it at least builds.

The only testing I have done is to run the testsuite on Linux (it passes) and tests t5300-pack-object.sh, t5302-pack-index.sh, t5510-fetch.sh and t6050-replace.sh on cygwin (running the full testsuite on cygwin takes *hours*) and again it passes.

On MinGW, however, the above tests all fail miserably! (They crash with that irritating 'git.exe failed do you want to send error report to Microsoft' dialog). I noticed that the 'counter_mutex' is not initialised or destroyed, and have (literally) just tested a patch which does this and ... it made no difference! :(

So, more debugging needs to be done on windows ...

ATB, Ramsay Jones

 builtin/index-pack.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)