[PATCH] Change the way labels are propagated when comparing memory through libc functions

[Lorenzo Martignoni]

Hi pcc,

(not necessarily for submission) 

My point is to start the discussion about what is the best way to propagate the labels in such functions. I personally believe the logic for propagating the labels should match the implementation (and that is what I tried to do in the attached patch).

http://llvm-reviews.chandlerc.com/D2252

Files:
  lib/dfsan/dfsan_custom.cc
  lib/dfsan/lit_tests/custom.c

Index: lib/dfsan/dfsan_custom.cc
===================================================================
--- lib/dfsan/dfsan_custom.cc
+++ lib/dfsan/dfsan_custom.cc
@@ -67,7 +67,7 @@
                                                   dfsan_label *ret_label) {
   for (size_t i = 0;; ++i) {
     if (s[i] == c || s[i] == 0) {
-      *ret_label = dfsan_union(dfsan_read_label(s, i+1), c_label);
+      *ret_label = dfsan_union(dfsan_read_label(s + i, 1), c_label);
       return s[i] == 0 ? 0 : const_cast<char *>(s+i);
     }
   }
@@ -81,13 +81,13 @@
   const char *cs1 = (const char *) s1, *cs2 = (const char *) s2;
   for (size_t i = 0; i != n; ++i) {
     if (cs1[i] != cs2[i]) {
-      *ret_label = dfsan_union(dfsan_read_label(cs1, i+1),
-                               dfsan_read_label(cs2, i+1));
+      *ret_label = dfsan_union(dfsan_read_label(cs1 + i, 1),
+                               dfsan_read_label(cs2 + i, 1));
       return cs1[i] - cs2[i];
     }
   }
-  *ret_label = dfsan_union(dfsan_read_label(cs1, n),
-                           dfsan_read_label(cs2, n));
+  *ret_label = dfsan_union(dfsan_read_label(cs1 + n - 1, 1),
+                           dfsan_read_label(cs2 + n - 1, 1));
   return 0;
 }
 
@@ -97,8 +97,8 @@
                                                 dfsan_label *ret_label) {
   for (size_t i = 0;; ++i) {
     if (s1[i] != s2[i] || s1[i] == 0 || s2[i] == 0) {
-      *ret_label = dfsan_union(dfsan_read_label(s1, i+1),
-                               dfsan_read_label(s2, i+1));
+      *ret_label = dfsan_union(dfsan_read_label(s1 + i, 1),
+                               dfsan_read_label(s2 + i, 1));
       return s1[i] - s2[i];
     }
   }
@@ -110,8 +110,8 @@
                   dfsan_label s2_label, dfsan_label *ret_label) {
   for (size_t i = 0;; ++i) {
     if (tolower(s1[i]) != tolower(s2[i]) || s1[i] == 0 || s2[i] == 0) {
-      *ret_label = dfsan_union(dfsan_read_label(s1, i+1),
-                               dfsan_read_label(s2, i+1));
+      *ret_label = dfsan_union(dfsan_read_label(s1 + i, 1),
+                               dfsan_read_label(s2 + i, 1));
       return s1[i] - s2[i];
     }
   }
@@ -129,9 +129,9 @@
   }
 
   for (size_t i = 0;; ++i) {
-    if (s1[i] != s2[i] || s1[i] == 0 || s2[i] == 0 || i == n-1) {
-      *ret_label = dfsan_union(dfsan_read_label(s1, i+1),
-                               dfsan_read_label(s2, i+1));
+    if (s1[i] != s2[i] || s1[i] == 0 || s2[i] == 0 || i == n - 1) {
+      *ret_label = dfsan_union(dfsan_read_label(s1 + i, 1),
+                               dfsan_read_label(s2 + i, 1));
       return s1[i] - s2[i];
     }
   }
@@ -150,8 +150,8 @@
   for (size_t i = 0;; ++i) {
     if (tolower(s1[i]) != tolower(s2[i]) || s1[i] == 0 || s2[i] == 0 ||
         i == n - 1) {
-      *ret_label = dfsan_union(dfsan_read_label(s1, i+1),
-                               dfsan_read_label(s2, i+1));
+      *ret_label = dfsan_union(dfsan_read_label(s1 + i, 1),
+                               dfsan_read_label(s2 + i, 1));
       return s1[i] - s2[i];
     }
   }
Index: lib/dfsan/lit_tests/custom.c
===================================================================
--- lib/dfsan/lit_tests/custom.c
+++ lib/dfsan/lit_tests/custom.c
@@ -179,7 +179,7 @@
 
   rv = strcasecmp(str1, str3);
   assert(rv == 0);
-  ASSERT_LABEL(rv, dfsan_union(i_label, j_label));
+  ASSERT_ZERO_LABEL(rv);
 }
 
 void test_strncasecmp() {
@@ -210,7 +210,7 @@
 
   crv = strchr(str1, 'x');
   assert(!crv);
-  ASSERT_LABEL(crv, i_label);
+  ASSERT_ZERO_LABEL(crv);
 }
 
 void test_calloc() {
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