compat: move strdup(3) replacement to its own file

Move our implementation of strdup(3) out of compat/nedmalloc/ and
allow it to be used independently from USE_NED_ALLOCATOR.  The
original nedmalloc doesn't come with strdup() and doesn't need it.
Only _users_ of nedmalloc need it, which was added when we imported
it to our compat/ hierarchy.

This reduces the difference of our copy of nedmalloc from the
original, making it easier to update, and allows for easier testing
and reusing of our version of strdup().

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -296,6 +296,11 @@ all::
 # Define USE_NED_ALLOCATOR if you want to replace the platforms default
 # memory allocators with the nedmalloc allocator written by Niall Douglas.
 #
+# Define OVERRIDE_STRDUP to override the libc version of strdup(3).
+# This is necessary when using a custom allocator in order to avoid
+# crashes due to allocation and free working on different 'heaps'.
+# It's defined automatically if USE_NED_ALLOCATOR is set.
+#
 # Define NO_REGEX if you have no or inferior regex support in your C library.
 #
 # Define HAVE_DEV_TTY if your system can open /dev/tty to interact with the
@@ -1442,8 +1447,14 @@ ifdef NATIVE_CRLF
 endif
 
 ifdef USE_NED_ALLOCATOR
-       COMPAT_CFLAGS += -Icompat/nedmalloc
-       COMPAT_OBJS += compat/nedmalloc/nedmalloc.o
+	COMPAT_CFLAGS += -Icompat/nedmalloc
+	COMPAT_OBJS += compat/nedmalloc/nedmalloc.o
+	OVERRIDE_STRDUP = YesPlease
+endif
+
+ifdef OVERRIDE_STRDUP
+	COMPAT_CFLAGS += -DOVERRIDE_STRDUP
+	COMPAT_OBJS += compat/strdup.o
 endif
 
 ifdef GIT_TEST_CMP_USE_COPIED_CONTEXT
@@ -1993,7 +2004,7 @@ endif
 
 ifdef USE_NED_ALLOCATOR
 compat/nedmalloc/nedmalloc.sp compat/nedmalloc/nedmalloc.o: EXTRA_CPPFLAGS = \
-	-DNDEBUG -DOVERRIDE_STRDUP -DREPLACE_SYSTEM_ALLOCATOR
+	-DNDEBUG -DREPLACE_SYSTEM_ALLOCATOR
 compat/nedmalloc/nedmalloc.sp: SPARSE_FLAGS += -Wno-non-pointer-null
 endif
 

compat/nedmalloc/nedmalloc.c

@@ -948,22 +948,6 @@ void **nedpindependent_comalloc(nedpool *p, size_t elems, size_t *sizes, void **
 	return ret;
 }
 
-#ifdef OVERRIDE_STRDUP
-/*
- * This implementation is purely there to override the libc version, to
- * avoid a crash due to allocation and free on different 'heaps'.
- */
-char *strdup(const char *s1)
-{
-	size_t len = strlen(s1) + 1;
-	char *s2 = malloc(len);
-
-	if (s2)
-		memcpy(s2, s1, len);
-	return s2;
-}
-#endif
-
 #if defined(__cplusplus)
 }
 #endif

compat/strdup.c

@@ -0,0 +1,11 @@
+#include "../git-compat-util.h"
+
+char *gitstrdup(const char *s1)
+{
+	size_t len = strlen(s1) + 1;
+	char *s2 = malloc(len);
+
+	if (s2)
+		memcpy(s2, s1, len);
+	return s2;
+}

git-compat-util.h

@@ -646,6 +646,14 @@ void *gitmemmem(const void *haystack, size_t haystacklen,
                 const void *needle, size_t needlelen);
 #endif
 
+#ifdef OVERRIDE_STRDUP
+#ifdef strdup
+#undef strdup
+#endif
+#define strdup gitstrdup
+char *gitstrdup(const char *s);
+#endif
+
 #ifdef NO_GETPAGESIZE
 #define getpagesize() sysconf(_SC_PAGESIZE)
 #endif