[libxml2] Use strcmp when fuzzing

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 9de7b94d4ffbd11814008a5aa529b4ca77564921
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Sat Aug 8 20:37:30 2020 +0200

    Use strcmp when fuzzing
    
    This should improve data-flow-guided fuzzing.

 xmlstring.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)
---
diff --git a/xmlstring.c b/xmlstring.c
index 8d2e06f66..e8a1e45d1 100644
--- a/xmlstring.c
+++ b/xmlstring.c
@@ -130,16 +130,18 @@ xmlCharStrdup(const char *cur) {
 
 int
 xmlStrcmp(const xmlChar *str1, const xmlChar *str2) {
-    register int tmp;
-
     if (str1 == str2) return(0);
     if (str1 == NULL) return(-1);
     if (str2 == NULL) return(1);
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+    return(strcmp((const char *)str1, (const char *)str2));
+#else
     do {
-        tmp = *str1++ - *str2;
+        int tmp = *str1++ - *str2;
         if (tmp != 0) return(tmp);
     } while (*str2++ != 0);
     return 0;
+#endif
 }
 
 /**
@@ -158,10 +160,14 @@ xmlStrEqual(const xmlChar *str1, const xmlChar *str2) {
     if (str1 == str2) return(1);
     if (str1 == NULL) return(0);
     if (str2 == NULL) return(0);
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+    return(strcmp((const char *)str1, (const char *)str2) == 0);
+#else
     do {
         if (*str1++ != *str2) return(0);
     } while (*str2++);
     return(1);
+#endif
 }
 
 /**
@@ -204,18 +210,15 @@ xmlStrQEqual(const xmlChar *pref, const xmlChar *name, const xmlChar *str) {
 
 int
 xmlStrncmp(const xmlChar *str1, const xmlChar *str2, int len) {
-    register int tmp;
-
     if (len <= 0) return(0);
     if (str1 == str2) return(0);
     if (str1 == NULL) return(-1);
     if (str2 == NULL) return(1);
-#ifdef __GNUC__
-    tmp = strncmp((const char *)str1, (const char *)str2, len);
-    return tmp;
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+    return(strncmp((const char *)str1, (const char *)str2, len));
 #else
     do {
-        tmp = *str1++ - *str2;
+        int tmp = *str1++ - *str2;
         if (tmp != 0 || --len == 0) return(tmp);
     } while (*str2++ != 0);
     return 0;