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From: Eric Wong <e@80x24.org>
To: raindrops-public@bogomips.org
Subject: [PATCH] avoid reading errno repeatedly
Date: Fri, 17 Mar 2017 01:57:34 +0000
Message-ID: <20170317015734.9783-1-e@80x24.org> (raw)

errno is in the thread-specific section and it is slightly
cheaper to read it once rather than twice.  Recent versions
of mainline Ruby itself follows the same pattern.
---
 ext/raindrops/raindrops.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/ext/raindrops/raindrops.c b/ext/raindrops/raindrops.c
index 390b8b8..9090839 100644
--- a/ext/raindrops/raindrops.c
+++ b/ext/raindrops/raindrops.c
@@ -117,7 +117,9 @@ retry:
 	r->drops = mmap(NULL, tmp,
 	                PROT_READ|PROT_WRITE, MAP_ANON|MAP_SHARED, -1, 0);
 	if (r->drops == MAP_FAILED) {
-		if ((errno == EAGAIN || errno == ENOMEM) && tries-- > 0) {
+		int err = errno;
+
+		if ((err == EAGAIN || err == ENOMEM) && tries-- > 0) {
 			rb_gc();
 			goto retry;
 		}
@@ -153,7 +155,9 @@ static void resize(struct raindrops *r, size_t new_rd_size)
 
 	rv = mremap(old_address, old_size, new_size, MREMAP_MAYMOVE);
 	if (rv == MAP_FAILED) {
-		if (errno == EAGAIN || errno == ENOMEM) {
+		int err = errno;
+
+		if (err == EAGAIN || err == ENOMEM) {
 			rb_gc();
 			rv = mremap(old_address, old_size, new_size, 0);
 		}
-- 
EW


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