From ac8360003ecfa1ec21295533c9213f17fd8e39bb Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Mon, 29 Jun 2020 07:23:16 +0900
Subject: Fix the bug that `mrbc` generates `a.rb.mrb` instead of `a.mrb`.

The bug was introduced by 9dfe50f1d.
---
 mrbgems/mruby-bin-mrbc/tools/mrbc/mrbc.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/mrbgems/mruby-bin-mrbc/tools/mrbc/mrbc.c b/mrbgems/mruby-bin-mrbc/tools/mrbc/mrbc.c
index 69c1095df..4d984e773 100644
--- a/mrbgems/mruby-bin-mrbc/tools/mrbc/mrbc.c
+++ b/mrbgems/mruby-bin-mrbc/tools/mrbc/mrbc.c
@@ -52,14 +52,27 @@ usage(const char *name)
 static char *
 get_outfilename(mrb_state *mrb, char *infile, const char *ext)
 {
-  size_t infilelen;
-  size_t flen;
+  size_t ilen, flen, elen;
   char *outfile;
+  char *p = NULL;
 
-  infilelen = strlen(infile);
-  flen = infilelen + strlen(ext) + 1;
-  outfile = (char*)mrb_malloc(mrb, flen);
-  snprintf(outfile, flen, "%s%s", infile, ext);
+  ilen = strlen(infile);
+  flen = ilen;
+  if (*ext) {
+    elen = strlen(ext);
+    if ((p = strrchr(infile, '.'))) {
+      ilen = p - infile;
+    }
+    flen += elen;
+  }
+  else {
+    flen = ilen;
+  }
+  outfile = (char*)mrb_malloc(mrb, flen+1);
+  strncpy(outfile, infile, ilen+1);
+  if (p) {
+    strncpy(outfile+ilen, ext, elen+1);
+  }
 
   return outfile;
 }
-- 
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