[PATCH 08/19] reduce stack usage from file names

[Eric Wong <e@80x24.org>]

Ruby source locations can be extremely long and use excessive
stack space.  Move it off stack for the temporary key lookup
to reduce the likelyhood of stack overflows.  No need to use
TSD (which is stored on stack with GCC anyways); as we have
GVL at that point.
---
 ext/mwrap/mwrap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ext/mwrap/mwrap.c b/ext/mwrap/mwrap.c
index 6109070..d08ebf0 100644
--- a/ext/mwrap/mwrap.c
+++ b/ext/mwrap/mwrap.c
@@ -291,6 +291,7 @@ static struct src_loc *update_stats_rcu(size_t size, uintptr_t caller)
 		const char *ptr = rb_source_location_cstr(&line);
 		size_t len;
 		size_t int_size = INT2STR_MAX;
+		static char buf[PATH_MAX + INT2STR_MAX + sizeof(*k) + 2];
 
 		generation = rb_gc_count();
 
@@ -298,7 +299,7 @@ static struct src_loc *update_stats_rcu(size_t size, uintptr_t caller)
 
 		/* avoid vsnprintf or anything which could call malloc here: */
 		len = strlen(ptr);
-		k = alloca(sizeof(*k) + len + 1 + int_size + 1);
+		k = (void *)buf;
 		k->total = size;
 		dst = mempcpy(k->k, ptr, len);
 		*dst++ = ':';
-- 
EW