diff --git a/src/runtime/cgo/gcc_darwin_amd64.c b/src/runtime/cgo/gcc_darwin_amd64.c
index 955b81da0b..dda9a1e2d8 100644
--- a/src/runtime/cgo/gcc_darwin_amd64.c
+++ b/src/runtime/cgo/gcc_darwin_amd64.c
@@ -14,12 +14,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	size_t size;
-
 	setg_gcc = setg;
-
-	size = pthread_get_stacksize_np(pthread_self());
-	g->stacklo = (uintptr)&size - size + 4096;
+	_cgo_set_stacklo(g, NULL);
 }
 
 
diff --git a/src/runtime/cgo/gcc_darwin_arm64.c b/src/runtime/cgo/gcc_darwin_arm64.c
index 5b77a4294a..f1344de8e1 100644
--- a/src/runtime/cgo/gcc_darwin_arm64.c
+++ b/src/runtime/cgo/gcc_darwin_arm64.c
@@ -127,12 +127,9 @@ init_working_dir()
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	size_t size;
-
 	//fprintf(stderr, "x_cgo_init = %p\n", &x_cgo_init); // aid debugging in presence of ASLR
 	setg_gcc = setg;
-	size = pthread_get_stacksize_np(pthread_self());
-	g->stacklo = (uintptr)&size - size + 4096;
+	_cgo_set_stacklo(g, NULL);
 
 #if TARGET_OS_IPHONE
 	darwin_arm_init_mach_exception_handler();
diff --git a/src/runtime/cgo/gcc_dragonfly_amd64.c b/src/runtime/cgo/gcc_dragonfly_amd64.c
index 0003414bf8..b5ae411d3d 100644
--- a/src/runtime/cgo/gcc_dragonfly_amd64.c
+++ b/src/runtime/cgo/gcc_dragonfly_amd64.c
@@ -16,14 +16,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_freebsd_386.c b/src/runtime/cgo/gcc_freebsd_386.c
index 9097a2af90..e56fad6a5b 100644
--- a/src/runtime/cgo/gcc_freebsd_386.c
+++ b/src/runtime/cgo/gcc_freebsd_386.c
@@ -16,14 +16,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 
diff --git a/src/runtime/cgo/gcc_freebsd_amd64.c b/src/runtime/cgo/gcc_freebsd_amd64.c
index 6071ec3909..d3c133fc76 100644
--- a/src/runtime/cgo/gcc_freebsd_amd64.c
+++ b/src/runtime/cgo/gcc_freebsd_amd64.c
@@ -18,7 +18,6 @@ void
 x_cgo_init(G *g, void (*setg)(void*))
 {
 	pthread_attr_t *attr;
-	size_t size;
 
 	// Deal with memory sanitizer/clang interaction.
 	// See gcc_linux_amd64.c for details.
@@ -27,10 +26,7 @@ x_cgo_init(G *g, void (*setg)(void*))
 	if (attr == NULL) {
 		fatalf("malloc failed: %s", strerror(errno));
 	}
-	pthread_attr_init(attr);
-	pthread_attr_getstacksize(attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(attr);
+	_cgo_set_stacklo(g, attr);
 	free(attr);
 }
 
diff --git a/src/runtime/cgo/gcc_freebsd_arm.c b/src/runtime/cgo/gcc_freebsd_arm.c
index 5f89978379..af398f8320 100644
--- a/src/runtime/cgo/gcc_freebsd_arm.c
+++ b/src/runtime/cgo/gcc_freebsd_arm.c
@@ -27,14 +27,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_freebsd_arm64.c b/src/runtime/cgo/gcc_freebsd_arm64.c
index dd8f888290..01f6a31c32 100644
--- a/src/runtime/cgo/gcc_freebsd_arm64.c
+++ b/src/runtime/cgo/gcc_freebsd_arm64.c
@@ -17,14 +17,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_freebsd_riscv64.c b/src/runtime/cgo/gcc_freebsd_riscv64.c
index 6ce5e656ab..7fe7972d2d 100644
--- a/src/runtime/cgo/gcc_freebsd_riscv64.c
+++ b/src/runtime/cgo/gcc_freebsd_riscv64.c
@@ -17,14 +17,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_libinit.c b/src/runtime/cgo/gcc_libinit.c
index 0b2cc25277..f6c930209e 100644
--- a/src/runtime/cgo/gcc_libinit.c
+++ b/src/runtime/cgo/gcc_libinit.c
@@ -82,6 +82,34 @@ _cgo_wait_runtime_init_done(void) {
 	return 0;
 }
 
+// _cgo_set_stacklo sets g->stacklo based on the stack size.
+// This is common code called from x_cgo_init, which is itself
+// called by rt0_go in the runtime package.
+void _cgo_set_stacklo(G *g, pthread_attr_t *pattr)
+{
+	pthread_attr_t attr;
+	size_t size;
+
+	// pattr can be passed in by the caller; see gcc_linux_amd64.c.
+	if (pattr == NULL) {
+		pattr = &attr;
+	}
+
+	pthread_attr_init(pattr);
+	pthread_attr_getstacksize(pattr, &size);
+
+	g->stacklo = (uintptr)(__builtin_frame_address(0)) - size + 4096;
+
+	// Sanity check the results now, rather than getting a
+	// morestack on g0 crash.
+	if (g->stacklo >= g->stackhi) {
+		fprintf(stderr, "runtime/cgo: bad stack bounds: lo=%p hi=%p\n", (void*)(g->stacklo), (void*)(g->stackhi));
+		abort();
+	}
+
+	pthread_attr_destroy(pattr);
+}
+
 // Store the g into a thread-specific value associated with the pthread key pthread_g.
 // And pthread_key_destructor will dropm when the thread is exiting.
 void x_cgo_bindm(void* g) {
diff --git a/src/runtime/cgo/gcc_linux_386.c b/src/runtime/cgo/gcc_linux_386.c
index 0ce9359616..13a5aa90de 100644
--- a/src/runtime/cgo/gcc_linux_386.c
+++ b/src/runtime/cgo/gcc_linux_386.c
@@ -17,14 +17,8 @@ void (*x_cgo_inittls)(void **tlsg, void **tlsbase) __attribute__((common));
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 
 	if (x_cgo_inittls) {
 		x_cgo_inittls(tlsg, tlsbase);
diff --git a/src/runtime/cgo/gcc_linux_amd64.c b/src/runtime/cgo/gcc_linux_amd64.c
index fb164c1a1d..34b70e77ca 100644
--- a/src/runtime/cgo/gcc_linux_amd64.c
+++ b/src/runtime/cgo/gcc_linux_amd64.c
@@ -20,7 +20,6 @@ void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
 	pthread_attr_t *attr;
-	size_t size;
 
 	/* The memory sanitizer distributed with versions of clang
 	   before 3.8 has a bug: if you call mmap before malloc, mmap
@@ -42,12 +41,7 @@ x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 	if (attr == NULL) {
 		fatalf("malloc failed: %s", strerror(errno));
 	}
-	pthread_attr_init(attr);
-	pthread_attr_getstacksize(attr, &size);
-	g->stacklo = (uintptr)__builtin_frame_address(0) - size + 4096;
-	if (g->stacklo >= g->stackhi)
-		fatalf("bad stack bounds: lo=%p hi=%p\n", g->stacklo, g->stackhi);
-	pthread_attr_destroy(attr);
+	_cgo_set_stacklo(g, attr);
 	free(attr);
 
 	if (x_cgo_inittls) {
diff --git a/src/runtime/cgo/gcc_linux_arm.c b/src/runtime/cgo/gcc_linux_arm.c
index 5e97a9ed31..6a7e3bea04 100644
--- a/src/runtime/cgo/gcc_linux_arm.c
+++ b/src/runtime/cgo/gcc_linux_arm.c
@@ -54,14 +54,8 @@ threadentry(void *v)
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 
 	if (x_cgo_inittls) {
 		x_cgo_inittls(tlsg, tlsbase);
diff --git a/src/runtime/cgo/gcc_linux_arm64.c b/src/runtime/cgo/gcc_linux_arm64.c
index dac45e418b..8b822fe8a3 100644
--- a/src/runtime/cgo/gcc_linux_arm64.c
+++ b/src/runtime/cgo/gcc_linux_arm64.c
@@ -57,7 +57,6 @@ void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
 	pthread_attr_t *attr;
-	size_t size;
 
 	/* The memory sanitizer distributed with versions of clang
 	   before 3.8 has a bug: if you call mmap before malloc, mmap
@@ -79,10 +78,7 @@ x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 	if (attr == NULL) {
 		fatalf("malloc failed: %s", strerror(errno));
 	}
-	pthread_attr_init(attr);
-	pthread_attr_getstacksize(attr, &size);
-	g->stacklo = (uintptr)&size - size + 4096;
-	pthread_attr_destroy(attr);
+	_cgo_set_stacklo(g, attr);
 	free(attr);
 
 	if (x_cgo_inittls) {
diff --git a/src/runtime/cgo/gcc_linux_loong64.c b/src/runtime/cgo/gcc_linux_loong64.c
index 96a06eb960..b7363ccd96 100644
--- a/src/runtime/cgo/gcc_linux_loong64.c
+++ b/src/runtime/cgo/gcc_linux_loong64.c
@@ -54,14 +54,8 @@ threadentry(void *v)
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 
 	if (x_cgo_inittls) {
 		x_cgo_inittls(tlsg, tlsbase);
diff --git a/src/runtime/cgo/gcc_linux_mips64x.c b/src/runtime/cgo/gcc_linux_mips64x.c
index c059fd1255..6f4b52e2b0 100644
--- a/src/runtime/cgo/gcc_linux_mips64x.c
+++ b/src/runtime/cgo/gcc_linux_mips64x.c
@@ -56,14 +56,8 @@ threadentry(void *v)
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 
 	if (x_cgo_inittls) {
 		x_cgo_inittls(tlsg, tlsbase);
diff --git a/src/runtime/cgo/gcc_linux_mipsx.c b/src/runtime/cgo/gcc_linux_mipsx.c
index 218b8fd6e1..f6470d66dc 100644
--- a/src/runtime/cgo/gcc_linux_mipsx.c
+++ b/src/runtime/cgo/gcc_linux_mipsx.c
@@ -56,15 +56,9 @@ threadentry(void *v)
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
 
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 
 	if (x_cgo_inittls) {
 		x_cgo_inittls(tlsg, tlsbase);
diff --git a/src/runtime/cgo/gcc_linux_riscv64.c b/src/runtime/cgo/gcc_linux_riscv64.c
index 99c2866de4..ee4981104a 100644
--- a/src/runtime/cgo/gcc_linux_riscv64.c
+++ b/src/runtime/cgo/gcc_linux_riscv64.c
@@ -54,14 +54,8 @@ threadentry(void *v)
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsg, void **tlsbase)
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 
 	if (x_cgo_inittls) {
 		x_cgo_inittls(tlsg, tlsbase);
diff --git a/src/runtime/cgo/gcc_linux_s390x.c b/src/runtime/cgo/gcc_linux_s390x.c
index bb600482e1..4b9f76c39e 100644
--- a/src/runtime/cgo/gcc_linux_s390x.c
+++ b/src/runtime/cgo/gcc_linux_s390x.c
@@ -16,14 +16,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsbase)
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_netbsd_386.c b/src/runtime/cgo/gcc_netbsd_386.c
index 5495f0fd72..b8cb5d0bc9 100644
--- a/src/runtime/cgo/gcc_netbsd_386.c
+++ b/src/runtime/cgo/gcc_netbsd_386.c
@@ -15,14 +15,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 
diff --git a/src/runtime/cgo/gcc_netbsd_amd64.c b/src/runtime/cgo/gcc_netbsd_amd64.c
index 9f4b031a08..94ff1f52bf 100644
--- a/src/runtime/cgo/gcc_netbsd_amd64.c
+++ b/src/runtime/cgo/gcc_netbsd_amd64.c
@@ -15,14 +15,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 
diff --git a/src/runtime/cgo/gcc_netbsd_arm.c b/src/runtime/cgo/gcc_netbsd_arm.c
index b0c80ea7c4..ca370f69c3 100644
--- a/src/runtime/cgo/gcc_netbsd_arm.c
+++ b/src/runtime/cgo/gcc_netbsd_arm.c
@@ -16,14 +16,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 
diff --git a/src/runtime/cgo/gcc_netbsd_arm64.c b/src/runtime/cgo/gcc_netbsd_arm64.c
index 694116ce70..c6961f5cbe 100644
--- a/src/runtime/cgo/gcc_netbsd_arm64.c
+++ b/src/runtime/cgo/gcc_netbsd_arm64.c
@@ -16,14 +16,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 
diff --git a/src/runtime/cgo/gcc_openbsd_386.c b/src/runtime/cgo/gcc_openbsd_386.c
index 127a1b683b..092da4a6d2 100644
--- a/src/runtime/cgo/gcc_openbsd_386.c
+++ b/src/runtime/cgo/gcc_openbsd_386.c
@@ -15,14 +15,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_openbsd_amd64.c b/src/runtime/cgo/gcc_openbsd_amd64.c
index 09d2750f3a..3f0b771c74 100644
--- a/src/runtime/cgo/gcc_openbsd_amd64.c
+++ b/src/runtime/cgo/gcc_openbsd_amd64.c
@@ -15,14 +15,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_openbsd_arm.c b/src/runtime/cgo/gcc_openbsd_arm.c
index 9a5757f0ad..2aec207e36 100644
--- a/src/runtime/cgo/gcc_openbsd_arm.c
+++ b/src/runtime/cgo/gcc_openbsd_arm.c
@@ -15,14 +15,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_openbsd_arm64.c b/src/runtime/cgo/gcc_openbsd_arm64.c
index abf9f6660c..a9af8a2d1f 100644
--- a/src/runtime/cgo/gcc_openbsd_arm64.c
+++ b/src/runtime/cgo/gcc_openbsd_arm64.c
@@ -15,14 +15,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_openbsd_mips64.c b/src/runtime/cgo/gcc_openbsd_mips64.c
index 79f039a373..fbf7ceb0c5 100644
--- a/src/runtime/cgo/gcc_openbsd_mips64.c
+++ b/src/runtime/cgo/gcc_openbsd_mips64.c
@@ -15,14 +15,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*))
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_ppc64x.c b/src/runtime/cgo/gcc_ppc64x.c
index bfdcf65014..98a654957b 100644
--- a/src/runtime/cgo/gcc_ppc64x.c
+++ b/src/runtime/cgo/gcc_ppc64x.c
@@ -18,14 +18,8 @@ static void (*setg_gcc)(void*);
 void
 x_cgo_init(G *g, void (*setg)(void*), void **tlsbase)
 {
-	pthread_attr_t attr;
-	size_t size;
-
 	setg_gcc = setg;
-	pthread_attr_init(&attr);
-	pthread_attr_getstacksize(&attr, &size);
-	g->stacklo = (uintptr)&attr - size + 4096;
-	pthread_attr_destroy(&attr);
+	_cgo_set_stacklo(g, NULL);
 }
 
 void
diff --git a/src/runtime/cgo/gcc_solaris_amd64.c b/src/runtime/cgo/gcc_solaris_amd64.c
index e89e844b1e..ebd945b2e3 100644
--- a/src/runtime/cgo/gcc_solaris_amd64.c
+++ b/src/runtime/cgo/gcc_solaris_amd64.c
@@ -27,6 +27,13 @@ x_cgo_init(G *g, void (*setg)(void*))
 	// See golang.org/issue/12210.
 	if(ctx.uc_stack.ss_size < 1024*1024)
 		g->stacklo -= 1024*1024 - ctx.uc_stack.ss_size;
+
+	// Sanity check the results now, rather than getting a
+	// morestack on g0 crash.
+	if (g->stacklo >= g->stackhi) {
+		fprintf(stderr, "runtime/cgo: bad stack bounds: lo=%p hi=%p\n", (void*)(g->stacklo), (void*)(g->stackhi));
+		abort();
+	}
 }
 
 void
diff --git a/src/runtime/cgo/libcgo_unix.h b/src/runtime/cgo/libcgo_unix.h
index a56a366f23..6d30769542 100644
--- a/src/runtime/cgo/libcgo_unix.h
+++ b/src/runtime/cgo/libcgo_unix.h
@@ -2,6 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+/*
+ * Initialize g->stacklo.
+ */
+extern void _cgo_set_stacklo(G *, pthread_attr_t*);
+
 /*
  * Call pthread_create, retrying on EAGAIN.
  */