Do not pass NULL to memcpy() in Buffer/String objects.

glibc and others seem tolerant of this but the behavior is undefined.

Found with -fsanitize=undefined.

src/common/type/buffer.c

@@ -112,7 +112,10 @@ bufDup(const Buffer *buffer)
 
     // Create object and copy data
     Buffer *this = bufNew(bufUsed(buffer));
+
+    if (bufUsed(buffer) != 0)
         memcpy(this->pub.buffer, buffer->pub.buffer, bufSize(this));
+
     this->pub.used = bufSize(this);
 
     FUNCTION_TEST_RETURN(this);

src/common/type/string.c

@@ -173,7 +173,9 @@ strNewBuf(const Buffer *buffer)
     String *this = strNewFixed(bufUsed(buffer));
 
     // Assign string
+    if (strSize(this) != 0)
         memcpy(this->pub.buffer, bufPtrConst(buffer), strSize(this));
+
     this->pub.buffer[strSize(this)] = 0;
 
     FUNCTION_TEST_RETURN(this);

test/src/module/common/typeBufferTest.c

@@ -29,6 +29,8 @@ testRun(void)
         TEST_ASSIGN(buffer, bufNewC("TEST-STR", sizeof("TEST-STR") - 1), "new buffer from string");
         TEST_RESULT_BOOL(memcmp(bufPtr(buffer), "TEST-STR", 8) == 0, true, "check buffer");
 
+        TEST_RESULT_UINT(bufSize(bufDup(bufNew(0))), 0, "duplicate empty buffer");
+
         TEST_RESULT_VOID(bufFree(buffer), "free buffer");
         TEST_RESULT_VOID(bufFree(bufNew(0)), "free empty buffer");
 

test/src/module/common/typeStringTest.c

@@ -49,6 +49,8 @@ testRun(void)
         TEST_RESULT_UINT(strlen(strZ(string)), 13, "check size with strlen()");
         TEST_RESULT_INT(strZNull(string)[2], 'a', "check character");
 
+        TEST_RESULT_UINT(strSize(strNewBuf(bufNew(0))), 0, "new string from empty buffer");
+
         TEST_RESULT_VOID(strFree(string), "free string");
 
         // -------------------------------------------------------------------------------------------------------------------------