ci: fix windows-build with GCC v12.x
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windows-build with GCC v12.x
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Git for Windows' SDK recently upgraded to GCC v12.x which points out that the `pos` variable might be used even after the corresponding memory was `realloc()`ed and therefore potentially no longer valid. Since a subset of this SDK is used in Git's CI/PR builds, we need to fix this to continue to be able to benefit from the CI/PR runs. Note: This bug has been with us since 2a6b149 (mingw: avoid using strbuf in syslog, 2011-10-06), and while it looks tempting to replace the hand-rolled string manipulation with a `strbuf`-based one, that commit's message explains why we cannot do that: The `syslog()` function is called as part of the function in `daemon.c` which is set as the `die()` routine, and since `strbuf_grow()` can call that function if it runs out of memory, this would cause a nasty infinite loop that we do not want to re-introduce. Signed-off-by: Johannes Schindelin <[email protected]> Signed-off-by: Junio C Hamano <[email protected]>
GCC v12.x complains thusly:
compat/nedmalloc/nedmalloc.c: In function 'DestroyCaches':
compat/nedmalloc/nedmalloc.c:326:12: error: the comparison will always
evaluate as 'true' for the address of 'caches'
will never be NULL [-Werror=address]
326 | if(p->caches)
| ^
compat/nedmalloc/nedmalloc.c:196:22: note: 'caches' declared here
196 | threadcache *caches[THREADCACHEMAXCACHES];
| ^~~~~~
... and it is correct, of course.
Signed-off-by: Johannes Schindelin <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>
Technically, the pointer difference `end - start` _could_ be negative,
and when cast to an (unsigned) `size_t` that would cause problems. In
this instance, the symptom is:
dir.c: In function 'git_url_basename':
dir.c:3087:13: error: 'memchr' specified bound [9223372036854775808, 0]
exceeds maximum object size 9223372036854775807
[-Werror=stringop-overread]
CC ewah/bitmap.o
3087 | if (memchr(start, '/', end - start) == NULL
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
While it is a bit far-fetched to think that `end` (which is defined as
`repo + strlen(repo)`) and `start` (which starts at `repo` and never
steps beyond the NUL terminator) could result in such a negative
difference, GCC has no way of knowing that.
See also https://gcc.gnu.org/bugzilla//show_bug.cgi?id=85783.
Let's just add a safety check, primarily for GCC's benefit.
Signed-off-by: Johannes Schindelin <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>
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This branch brings a couple of fixes to be able to compile Git in `DEVELOPER=1` mode again. The only remaining issue is a local variable's address in `run_active_slot()` in `http.c` that is assigned to a struct that is still valid after the function scope was left. Junio wanted to do this differently from my proposed solution, and we'll merge Junio's work-around next. Signed-off-by: Johannes Schindelin <[email protected]>
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In http.c, the run_active_slot() function allows the given "slot" to make progress by calling step_active_slots() in a loop repeatedly, and the loop is not left until the request held in the slot completes. Ages ago, we used to use the slot->in_use member to get out of the loop, which misbehaved when the request in "slot" completes (at which time, the result of the request is copied away from the slot, and the in_use member is cleared, making the slot ready to be reused), and the "slot" gets reused to service a different request (at which time, the "slot" becomes in_use again, even though it is for a different request). The loop terminating condition mistakenly thought that the original request has yet to be completed. Today's code, after baa7b67 (HTTP slot reuse fixes, 2006-03-10) fixed this issue, uses a separate "slot->finished" member that is set in run_active_slot() to point to an on-stack variable, and the code that completes the request in finish_active_slot() clears the on-stack variable via the pointer to signal that the particular request held by the slot has completed. It also clears the in_use member (as before that fix), so that the slot itself can safely be reused for an unrelated request. One thing that is not quite clean in this arrangement is that, unless the slot gets reused, at which point the finished member is reset to NULL, the member keeps the value of &finished, which becomes a dangling pointer into the stack when run_active_slot() returns. Clear the finished member before the control leaves the function, which has a side effect of unconfusing compilers like recent GCC 12 that is over-eager to warn against such an assignment. Signed-off-by: Junio C Hamano <[email protected]>
This work-around shuts up GCC when it complains about a local variable's address being assigned to a struct that lives on after returning from the function. Technically, GCC is wrong not to complain that the pointer could have been copied and used later, but hey, the code compiles so we're happy. Signed-off-by: Johannes Schindelin <[email protected]>
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A recent update of GCC in Git for Windows' SDK (a subset of which is used in Git's CI/PR builds) broke the build. Lets' fix it.
This is a companion of gitgitgadget#1238.