_swab failed if src == dest, plus some testcases.

dlls/msvcrt/string.c

@@ -106,9 +106,11 @@ void MSVCRT__swab(char* src, char* dst, int len)
     len = (unsigned)len >> 1;
 
     while (len--) {
-      *dst++ = src[1];
-      *dst++ = *src++;
-      src++;
+      char s0 = src[0];
+      char s1 = src[1];
+      *dst++ = s1;
+      *dst++ = s0;
+      src = src + 2;
     }
   }
 }

dlls/msvcrt/tests/string.c

@@ -29,6 +29,50 @@ static int* (*pmemcmp)(void *, const void *, size_t n);
 #define SETNOFAIL(x,y) x = (void*)GetProcAddress(hMsvcrt,y)
 #define SET(x,y) SETNOFAIL(x,y); ok(x != NULL, "Export '%s' not found\n", y)
 
+static void test_swab( void ) {
+    char original[]  = "BADCFEHGJILKNMPORQTSVUXWZY@#";
+    char expected1[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ@#";
+    char expected2[] = "ABCDEFGHIJKLMNOPQRSTUVWX$";
+    char expected3[] = "$";
+    
+    char from[30];
+    char to[30];
+    
+    int testsize;
+    
+    /* Test 1 - normal even case */                               
+    memset(to,'$', sizeof(to));
+    memset(from,'@', sizeof(from));
+    testsize = 26;
+    memcpy(from, original, testsize);
+    _swab( from, to, testsize );
+    ok(memcmp(to,expected1,testsize) == 0, "Testing even size %d returned '%*.*s'\n", testsize, testsize, testsize, to);
+
+    /* Test 2 - uneven case  */                               
+    memset(to,'$', sizeof(to));
+    memset(from,'@', sizeof(from));
+    testsize = 25;
+    memcpy(from, original, testsize);
+    _swab( from, to, testsize );
+    ok(memcmp(to,expected2,testsize) == 0, "Testing odd size %d returned '%*.*s'\n", testsize, testsize, testsize, to);
+
+    /* Test 3 - from = to */                               
+    memset(to,'$', sizeof(to));
+    memset(from,'@', sizeof(from));
+    testsize = 26;
+    memcpy(to, original, testsize);
+    _swab( to, to, testsize );
+    ok(memcmp(to,expected1,testsize) == 0, "Testing overlapped size %d returned '%*.*s'\n", testsize, testsize, testsize, to);
+
+    /* Test 4 - 1 bytes */                               
+    memset(to,'$', sizeof(to));
+    memset(from,'@', sizeof(from));
+    testsize = 1;
+    memcpy(from, original, testsize);
+    _swab( from, to, testsize );
+    ok(memcmp(to,expected3,testsize) == 0, "Testing small size %d returned '%*.*s'\n", testsize, testsize, testsize, to);
+}
+
 
 START_TEST(string)
 {
@@ -48,4 +92,7 @@ START_TEST(string)
     pmemcpy((char*)mem+5, mem,nLen+1);
     ok(pmemcmp((char*)mem+5,xilstring, nLen) == 0, 
        "Got result %s\n",(char*)mem+5);
+
+    /* Test _swab function */
+    test_swab();
 }