From 330bedfb47b114d69d0ca21c2802cacb295de08d Mon Sep 17 00:00:00 2001
From: Nicholas Marriott <nicholas.marriott@gmail.com>
Date: Sun, 12 Jul 2026 13:26:25 +0100
Subject: [PATCH] Build with ASAN on macOS by default.

---
 Makefile.am  |  3 ++-
 configure.ac |  2 +-
 grid.c       |  3 +++
 tmux.c       | 18 ++++++++++++++++++
 4 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/Makefile.am b/Makefile.am
index d985e510d..84bdbdb2a 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -43,7 +43,8 @@ AM_CPPFLAGS += -DDEBUG
 endif
 AM_CPPFLAGS += -iquote.
 if IS_ASAN
-AM_CFLAGS += -fsanitize=address
+AM_CPPFLAGS += -DASAN
+AM_CFLAGS += -fsanitize=address -fno-omit-frame-pointer
 AM_LDFLAGS += -fsanitize=address
 endif
 endif
diff --git a/configure.ac b/configure.ac
index 6abb2d9d5..c118800b8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -78,7 +78,7 @@ AC_ARG_ENABLE(
 	asan,
 	AS_HELP_STRING(--enable-asan, enable ASAN build flags),
 	,
-	enable_asan=no
+	[case "x$host_os" in *darwin*) enable_asan=yes;; esac]
 )
 AM_CONDITIONAL(IS_ASAN, test "x$enable_asan" = xyes)
 
diff --git a/grid.c b/grid.c
index d03352f08..99d5371a9 100644
--- a/grid.c
+++ b/grid.c
@@ -366,6 +366,9 @@ grid_create(u_int sx, u_int sy, u_int hlimit)
 	if (gd->sy != 0)
 		gd->linedata = xcalloc(gd->sy, sizeof *gd->linedata);
 
+#ifdef __APPLE__
+	assert(gd->hsize == 0);
+#endif
 	grid_check_is_clear(gd);
 	return (gd);
 }
diff --git a/tmux.c b/tmux.c
index 132c39217..3739b6008 100644
--- a/tmux.c
+++ b/tmux.c
@@ -49,6 +49,24 @@ static char		*make_label(const char *, char **);
 static int		 areshell(const char *);
 static const char	*getshell(void);
 
+#ifdef ASAN
+__attribute__((used)) const char *__asan_default_options(void);
+__attribute__((used)) const char *
+__asan_default_options(void)
+{
+	return (
+	    "abort_on_error=1:"
+	    "halt_on_error=1:"
+	    "detect_leaks=0:"
+	    "detect_stack_use_after_return=1:"
+	    "strict_string_checks=1:"
+	    "check_initialization_order=1:"
+	    "log_path=/tmp/tmux-asan:"
+	    "log_exe_name=1"
+	);
+}
+#endif
+
 static __dead void
 usage(int status)
 {