devel/libgit2: fix build with clang 16

Clang 16 has a new error about incompatible function types, which shows
up when building devel/libgit2:

  /wrkdirs/usr/ports/devel/libgit2/work/libgit2-1.5.2/src/util/util.c:731:28: error: incompatible function pointer types passing 'int (void *, const void *, const void *)' to parameter of type 'int (*)(const void *, const void *, void *)' [-Wincompatible-function-pointer-types]
          qsort_s(els, nel, elsize, git__qsort_r_glue_cmp, &glue);
                                    ^~~~~~~~~~~~~~~~~~~~~
  /usr/include/stdlib.h:397:11: note: passing argument to parameter here
      int (*)(const void *, const void *, void *), void *);
            ^

Clang is indeed right, as the version of qsort_s(3) in FreeBSD 13 and
later has the 'void *payload' parameter last:

  errno_t  qsort_s(void *, rsize_t, rsize_t,
      int (*)(const void *, const void *, void *), void *);

This could be fixed by putting the arguments in the right place for
qsort_s(3), but it turns out the rabbit hole goes a bit deeper: on
14-CURRENT, libgit2's CMake configuration is not able to detect
qsort_r(3), which is actually why it chooses qsort_s():

  -- Checking prototype qsort_r for GIT_QSORT_R_BSD
  -- Checking prototype qsort_r for GIT_QSORT_R_BSD - False
  -- Checking prototype qsort_r for GIT_QSORT_R_GNU
  -- Checking prototype qsort_r for GIT_QSORT_R_GNU - False
  -- Looking for qsort_s
  -- Looking for qsort_s - found

The problem with the GIT_QSORT_R_BSD detection is due to the check in
libgit2's src/CMakeLists.txt, where it does:

  check_prototype_definition(qsort_r
          "void qsort_r(void *base, size_t nmemb, size_t size, void
          *thunk, int (*compar)(void *, const void *, const void *))"
          "" "stdlib.h" GIT_QSORT_R_BSD)

and CMake attempts to define a function with a similar prototype in its
test program, which then fails to compile, at least on 14-CURRENT:

  /wrkdirs/share/dim/ports/devel/libgit2/work/.build/CMakeFiles/CMakeScratch/TryCompile-tILE28/CheckPrototypeDefinition.c:14:6:
  error: expected identifier or '('
  void qsort_r(void *base, size_t nmemb, size_t size, void *thunk, int
  (*compar)(void *, const void *, const void *)) {
       ^
  /usr/include/stdlib.h:357:5: note: expanded from macro 'qsort_r'
      __generic(arg5, int (*)(void *, const void *, const void *),
       \\
      ^
  /usr/include/sys/cdefs.h:323:2: note: expanded from macro '__generic'
          _Generic(expr, t: yes, default: no)
          ^

This is because in https://cgit.freebsd.org/src/commit/?id=af3c78886fd8d
Ed Schouten changed the prototype of qsort_r(3) to match POSIX, using a
C11 _Generic macro. When CMake tries to compile its own custom
definition of qsort_r, that fails with the above compile error, because
the macro gets expanded in place of the function declaration.

So the summarized situation is:

* On 12.x and 13.x, qsort_r(3) is a plain function, and uses the old
  comparison function type: 'int (*compar)(void *thunk, const void
  *elem1, const void *elem2)'.
  Therefore, CMake detects GIT_QSORT_R_BSD, and libgit2's
  src/util/util.c uses the correct comparison function type.
* On 14.x, qsort_r(3) is a macro, and uses the POSIX comparison function
  type: 'int (*compar)(const void *elem1, const void *elem2, void *thunk)'.
  Therefore, CMake fails to detect GIT_QSORT_R_BSD, and detects
  GIT_QSORT_S instead, and libgit2's src/util/util.c uses an incorrect
  comparison function type.

I submitted https://github.com/libgit2/libgit2/pull/6555 and
https://github.com/libgit2/libgit2/pull/6558 upstream to remedy the
situation and correctly detect all qsort variants, and these were merged
with a few minor changes.

This is an adjusted version of the upstream commits that applies on top
of libgit-1.5.2.

PR:		271234
Approved by:	mfechner (maintainer)
MFH:		2023Q2

2 files changed, 146 insertions, 0 deletions

diff --git a/devel/libgit2/Makefile b/devel/libgit2/Makefile
index 68c9edb1607e..8d2a05ddd981 100644
--- a/devel/libgit2/Makefile
+++ b/devel/libgit2/Makefile
@@ -6,6 +6,7 @@
 PORTNAME=	libgit2
 DISTVERSIONPREFIX=	v
 DISTVERSION=	1.5.2
+PORTREVISION=	1
 CATEGORIES=	devel
 
 MAINTAINER=	mfechner@FreeBSD.org
diff --git a/devel/libgit2/files/patch-github-pr6555 b/devel/libgit2/files/patch-github-pr6555
new file mode 100644
index 000000000000..99856eb18372
--- /dev/null
+++ b/devel/libgit2/files/patch-github-pr6555
@@ -0,0 +1,145 @@
+--- CMakeLists.txt.orig	2023-02-15 10:03:30 UTC
++++ CMakeLists.txt
+@@ -96,7 +96,7 @@ include(CheckStructHasMember)
+ include(CheckFunctionExists)
+ include(CheckSymbolExists)
+ include(CheckStructHasMember)
+-include(CheckPrototypeDefinition)
++include(CheckPrototypeDefinitionSafe)
+ include(AddCFlagIfSupported)
+ include(FindPkgLibraries)
+ include(FindThreads)
+--- cmake/CheckPrototypeDefinitionSafe.cmake.orig	2023-05-14 12:22:20 UTC
++++ cmake/CheckPrototypeDefinitionSafe.cmake
+@@ -0,0 +1,16 @@
++include(CheckPrototypeDefinition)
++
++function(check_prototype_definition_safe function prototype return header variable)
++	# temporarily save CMAKE_C_FLAGS and disable warnings about unused
++	# unused functions and parameters, otherwise they will always fail
++	# if ENABLE_WERROR is on
++	set(SAVED_CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
++
++	disable_warnings(unused-function)
++	disable_warnings(unused-parameter)
++
++	check_prototype_definition("${function}" "${prototype}" "${return}" "${header}" "${variable}")
++
++	# restore CMAKE_C_FLAGS
++	set(CMAKE_C_FLAGS "${SAVED_CMAKE_C_FLAGS}")
++endfunction()
+--- src/CMakeLists.txt.orig	2023-02-15 10:03:30 UTC
++++ src/CMakeLists.txt
+@@ -58,15 +58,29 @@ add_feature_info(futimens GIT_USE_FUTIMENS "futimens s
+ 
+ # qsort
+ 
+-check_prototype_definition(qsort_r
+-	"void qsort_r(void *base, size_t nmemb, size_t size, void *thunk, int (*compar)(void *, const void *, const void *))"
+-	"" "stdlib.h" GIT_QSORT_R_BSD)
++# old-style FreeBSD qsort_r() has the 'context' parameter as the first argument
++# of the comparison function:
++check_prototype_definition_safe(qsort_r
++	"void (qsort_r)(void *base, size_t nmemb, size_t size, void *context, int (*compar)(void *, const void *, const void *))"
++	"" "stdlib.h" GIT_QSORT_BSD)
+ 
+-check_prototype_definition(qsort_r
+-	"void qsort_r(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *, void *), void *arg)"
+-	"" "stdlib.h" GIT_QSORT_R_GNU)
++# GNU or POSIX qsort_r() has the 'context' parameter as the last argument of the
++# comparison function:
++check_prototype_definition_safe(qsort_r
++	"void (qsort_r)(void *base, size_t nmemb, size_t size, int (*compar)(const void *, const void *, void *), void *context)"
++	"" "stdlib.h" GIT_QSORT_GNU)
+ 
+-check_function_exists(qsort_s GIT_QSORT_S)
++# C11 qsort_s() has the 'context' parameter as the last argument of the
++# comparison function, and returns an error status:
++check_prototype_definition_safe(qsort_s
++	"errno_t (qsort_s)(void *base, rsize_t nmemb, rsize_t size, int (*compar)(const void *, const void *, void *), void *context)"
++	"0" "stdlib.h" GIT_QSORT_C11)
++
++# MSC qsort_s() has the 'context' parameter as the first argument of the
++# comparison function, and as the last argument of qsort_s():
++check_prototype_definition_safe(qsort_s
++	"void (qsort_s)(void *base, size_t num, size_t width, int (*compare )(void *, const void *, const void *), void *context)"
++	"" "stdlib.h" GIT_QSORT_MSC)
+ 
+ # random / entropy data
+ 
+--- src/features.h.in.orig	2023-02-15 10:03:30 UTC
++++ src/features.h.in
+@@ -24,9 +24,10 @@
+ #cmakedefine GIT_REGEX_PCRE2
+ #cmakedefine GIT_REGEX_BUILTIN 1
+ 
+-#cmakedefine GIT_QSORT_R_BSD
+-#cmakedefine GIT_QSORT_R_GNU
+-#cmakedefine GIT_QSORT_S
++#cmakedefine GIT_QSORT_BSD
++#cmakedefine GIT_QSORT_GNU
++#cmakedefine GIT_QSORT_C11
++#cmakedefine GIT_QSORT_MSC
+ 
+ #cmakedefine GIT_SSH 1
+ #cmakedefine GIT_SSH_MEMORY_CREDENTIALS 1
+--- src/util/util.c.orig	2023-02-15 10:03:30 UTC
++++ src/util/util.c
+@@ -18,7 +18,7 @@
+ # endif
+ # include <windows.h>
+ 
+-# ifdef GIT_QSORT_S
++# ifdef GIT_QSORT_MSC
+ #  include <search.h>
+ # endif
+ #endif
+@@ -673,7 +673,7 @@ size_t git__unescape(char *str)
+ 	return (pos - str);
+ }
+ 
+-#if defined(GIT_QSORT_S) || defined(GIT_QSORT_R_BSD)
++#if defined(GIT_QSORT_MSC) || defined(GIT_QSORT_BSD)
+ typedef struct {
+ 	git__sort_r_cmp cmp;
+ 	void *payload;
+@@ -688,9 +688,11 @@ static int GIT_LIBGIT2_CALL git__qsort_r_glue_cmp(
+ #endif
+ 
+ 
+-#if !defined(GIT_QSORT_R_BSD) && \
+-	!defined(GIT_QSORT_R_GNU) && \
+-	!defined(GIT_QSORT_S)
++#if !defined(GIT_QSORT_BSD) && \
++    !defined(GIT_QSORT_GNU) && \
++    !defined(GIT_QSORT_C11) && \
++    !defined(GIT_QSORT_MSC)
++
+ static void swap(uint8_t *a, uint8_t *b, size_t elsize)
+ {
+ 	char tmp[256];
+@@ -716,17 +718,20 @@ static void insertsort(
+ 		for (j = i; j > base && cmp(j, j - elsize, payload) < 0; j -= elsize)
+ 			swap(j, j - elsize, elsize);
+ }
++
+ #endif
+ 
+ void git__qsort_r(
+ 	void *els, size_t nel, size_t elsize, git__sort_r_cmp cmp, void *payload)
+ {
+-#if defined(GIT_QSORT_R_BSD)
++#if defined(GIT_QSORT_GNU)
++	qsort_r(els, nel, elsize, cmp, payload);
++#elif defined(GIT_QSORT_C11)
++	qsort_s(els, nel, elsize, cmp, payload);
++#elif defined(GIT_QSORT_BSD)
+ 	git__qsort_r_glue glue = { cmp, payload };
+ 	qsort_r(els, nel, elsize, &glue, git__qsort_r_glue_cmp);
+-#elif defined(GIT_QSORT_R_GNU)
+-	qsort_r(els, nel, elsize, cmp, payload);
+-#elif defined(GIT_QSORT_S)
++#elif defined(GIT_QSORT_MSC)
+ 	git__qsort_r_glue glue = { cmp, payload };
+ 	qsort_s(els, nel, elsize, git__qsort_r_glue_cmp, &glue);
+ #else