handle memmove of 0

2 files changed, 4 insertions, 0 deletions

diff --git a/src/preamble.js b/src/preamble.js
index 8c954d0d..4eb99d18 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -388,6 +388,7 @@ _memcpy = _llvm_memcpy_i64 = _llvm_memcpy_p0i8_p0i8_i32 = _llvm_memcpy_p0i8_p0i8
 
 function _llvm_memmove_i32(dest, src, num, idunno) {
   // not optimized!
+  if (num === 0) return; // will confuse malloc if 0
   var tmp = _malloc(num);
   _memcpy(tmp, src, num);
   _memcpy(dest, tmp, num);
diff --git a/tests/runner.py b/tests/runner.py
index ef6f024d..56add2db 100644
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -385,6 +385,9 @@ if 'benchmark' not in sys.argv:
 
           int main(int argc, char **argv)
           {
+            int x = 5, y = 9, magic = 7; // fool compiler with magic
+            memmove(&x, &y, magic-7); // 0 should not crash us
+
             printf("*%d\\n", argc);
             puts(argv[1]);
             puts(argv[2]);