Support static linking of jemalloc with glibc

glibc defines its malloc implementation with several weak and strong
symbols:

strong_alias (__libc_calloc, __calloc) weak_alias (__libc_calloc, calloc)
strong_alias (__libc_free, __cfree) weak_alias (__libc_free, cfree)
strong_alias (__libc_free, __free) strong_alias (__libc_free, free)
strong_alias (__libc_malloc, __malloc) strong_alias (__libc_malloc, malloc)

The issue is not with the weak symbols, but that other parts of glibc
depend on __libc_malloc explicitly.  Defining them in terms of jemalloc
API's allows the linker to drop glibc's malloc.o completely from the link,
and static linking no longer results in symbol collisions.

Another wrinkle: jemalloc during initialization calls sysconf to
get the number of CPU's.  GLIBC allocates for the first time before
setting up isspace (and other related) tables, which are used by
sysconf.  Instead, use the pthread API to get the number of
CPUs with GLIBC, which seems to work.

This resolves #442.

2 files changed, 34 insertions, 0 deletions

diff --git a/include/jemalloc/internal/jemalloc_internal_decls.h b/include/jemalloc/internal/jemalloc_internal_decls.h
index 910b2fc..1d7f207 100644
--- a/include/jemalloc/internal/jemalloc_internal_decls.h
+++ b/include/jemalloc/internal/jemalloc_internal_decls.h
@@ -17,6 +17,9 @@
 #    include <sys/uio.h>
 #  endif
 #  include <pthread.h>
+#  ifdef JEMALLOC_GLIBC_MALLOC_HOOK
+#    include <sched.h>
+#  endif
 #  include <errno.h>
 #  include <sys/time.h>
 #  include <time.h>
diff --git a/src/jemalloc.c b/src/jemalloc.c
index 1f951e2..816cc73 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -749,6 +749,18 @@ malloc_ncpus(void)
 	SYSTEM_INFO si;
 	GetSystemInfo(&si);
 	result = si.dwNumberOfProcessors;
+#elif defined(JEMALLOC_GLIBC_MALLOC_HOOK)
+	/*
+	 * glibc's sysconf() uses isspace().  glibc allocates for the first time
+	 * *before* setting up the isspace tables.  Therefore we need a
+	 * different method to get the number of CPUs.
+	 */
+	{
+		cpu_set_t set;
+
+		pthread_getaffinity_np(pthread_self(), sizeof(set), &set);
+		result = CPU_COUNT(&set);
+	}
 #else
 	result = sysconf(_SC_NPROCESSORS_ONLN);
 #endif
@@ -1882,6 +1894,25 @@ JEMALLOC_EXPORT void *(*__realloc_hook)(void *ptr, size_t size) = je_realloc;
 JEMALLOC_EXPORT void *(*__memalign_hook)(size_t alignment, size_t size) =
     je_memalign;
 # endif
+
+/*
+ * To enable static linking with glibc, the libc specific malloc interface must
+ * be implemented also, so none of glibc's malloc.o functions are added to the
+ * link.
+ */
+#define	ALIAS(je_fn)	__attribute__((alias (#je_fn), used))
+/* To force macro expansion of je_ prefix before stringification. */
+#define	PREALIAS(je_fn)  ALIAS(je_fn)
+void	*__libc_malloc(size_t size) PREALIAS(je_malloc);
+void	__libc_free(void* ptr) PREALIAS(je_free);
+void	*__libc_realloc(void* ptr, size_t size) PREALIAS(je_realloc);
+void	*__libc_calloc(size_t n, size_t size) PREALIAS(je_calloc);
+void	*__libc_memalign(size_t align, size_t s) PREALIAS(je_memalign);
+void	*__libc_valloc(size_t size) PREALIAS(je_valloc);
+int	__posix_memalign(void** r, size_t a, size_t s)
+    PREALIAS(je_posix_memalign);
+#undef PREALIAS
+#undef ALIAS
 #endif
 
 /*