From 9a17437558e42aa1da372b515ba8bc18067d578c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lourens=20Naud=C3=A9?= <lourens@bearmetal.eu>
Date: Tue, 26 Nov 2019 13:07:49 +0000
Subject: Right size literal regular expression buffers on compile

---
 regcomp.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/regcomp.c b/regcomp.c
index df7f73bac5..7799e1d952 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -138,6 +138,25 @@ bitset_on_num(BitSetRef bs)
 }
 #endif
 
+// Attempt to right size allocated buffers for a regex post compile
+static void
+onig_reg_resize(regex_t *reg)
+{
+  resize:
+    if (reg->alloc > reg->used) {
+      unsigned char *new_ptr = xrealloc(reg->p, reg->used);
+      // Skip the right size optimization if memory allocation fails
+      if (new_ptr) {
+        reg->alloc = reg->used;
+        reg->p = new_ptr;
+      }
+    }
+    if (reg->chain) {
+      reg = reg->chain;
+      goto resize;
+    }
+}
+
 extern int
 onig_bbuf_init(BBuf* buf, OnigDistance size)
 {
@@ -5886,6 +5905,7 @@ onig_compile(regex_t* reg, const UChar* pattern, const UChar* pattern_end,
 #endif
 
  end:
+  onig_reg_resize(reg);
   return r;
 
  err_unset:
-- 
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