When commons were deprecated, noone noticed that malloc_options in static

binaries had become unlinkable. Change the libc definition to weak to solve
that, and to "const char * const" so that noone will try to set it late.
It must be stable before the first malloc() call, which could be before
main()...
discussion with otto, kettenis, tedu

2 files changed, 10 insertions, 7 deletions

diff --git a/src/lib/libc/stdlib/malloc.3 b/src/lib/libc/stdlib/malloc.3
index bea5575bf8..b0c6fb782b 100644
--- a/src/lib/libc/stdlib/malloc.3
+++ b/src/lib/libc/stdlib/malloc.3
@@ -30,9 +30,9 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.\"     $OpenBSD: malloc.3,v 1.142 2024/08/03 20:09:24 guenther Exp $
+.\"     $OpenBSD: malloc.3,v 1.143 2025/05/23 00:40:05 deraadt Exp $
 .\"
-.Dd $Mdocdate: August 3 2024 $
+.Dd $Mdocdate: May 23 2025 $
 .Dt MALLOC 3
 .Os
 .Sh NAME
@@ -69,7 +69,8 @@
 .Fn malloc_conceal "size_t size"
 .Ft void *
 .Fn calloc_conceal "size_t nmemb" "size_t size"
-.Vt char *malloc_options ;
+.Vt const char * const
+.Va malloc_options ;
 .Sh DESCRIPTION
 The standard functions
 .Fn malloc ,
@@ -265,7 +266,7 @@ value of the
 .Xr sysctl 2 ,
 next checks the environment for a variable called
 .Ev MALLOC_OPTIONS ,
-and finally looks at the global variable
+and finally looks at the pre-initialized global variable
 .Va malloc_options
 in the program.
 Each is scanned for the flags documented below.
diff --git a/src/lib/libc/stdlib/malloc.c b/src/lib/libc/stdlib/malloc.c
index cad8e5d6a1..fa36a3a7f3 100644
--- a/src/lib/libc/stdlib/malloc.c
+++ b/src/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: malloc.c,v 1.297 2024/09/20 02:00:46 jsg Exp $        */
+/*      $OpenBSD: malloc.c,v 1.298 2025/05/23 00:40:05 deraadt Exp $    */
 /*
  * Copyright (c) 2008, 2010, 2011, 2016, 2023 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -264,7 +264,8 @@ static union {
                 __attribute__((section(".openbsd.mutable")));
 #define mopts   malloc_readonly.mopts
 
-char            *malloc_options;        /* compile-time options */
+/* compile-time options */
+const char *const malloc_options __attribute__((weak));
 
 static __dead void wrterror(struct dir_info *d, char *msg, ...)
     __attribute__((__format__ (printf, 2, 3)));
@@ -501,7 +502,8 @@ omalloc_parseopt(char opt)
 static void
 omalloc_init(void)
 {
-        char *p, *q, b[16];
+        const char *p;
+        char *q, b[16];
         int i, j;
         const int mib[2] = { CTL_VM, VM_MALLOC_CONF };
         size_t sb;