add strncmp() wrapper

Author: tiedaoxiaotubie

runtime/LibcWrappers.cpp

@@ -633,4 +633,30 @@ int SYM(strcmp)(const char *a, const char *b) {
                               reinterpret_cast<uintptr_t>(SYM(strcmp)));
     return result;
 }
+
+int SYM(strncmp)(const char *a, const char *b, size_t n) {
+    tryAlternative(a, _sym_get_parameter_expression(0), SYM(strncmp));
+    tryAlternative(b, _sym_get_parameter_expression(1), SYM(strncmp));
+    tryAlternative(n, _sym_get_parameter_expression(2), SYM(strncmp));
+
+    auto result = strncmp(a, b, n);
+    _sym_set_return_expression(nullptr);
+
+    if (isConcrete(a, n) && isConcrete(b, n))
+        return result;
+
+    auto aShadowIt = ReadOnlyShadow(a, n).begin_non_null();
+    auto bShadowIt = ReadOnlyShadow(b, n).begin_non_null();
+    auto *allEqual = _sym_build_equal(*aShadowIt, *bShadowIt);
+    for (size_t i = 1; i < n; i++) {
+        ++aShadowIt;
+        ++bShadowIt;
+        allEqual =
+                _sym_build_bool_and(allEqual, _sym_build_equal(*aShadowIt, *bShadowIt));
+    }
+
+    _sym_push_path_constraint(allEqual, result == 0,
+                              reinterpret_cast<uintptr_t>(SYM(strncmp)));
+    return result;
+}
 }

runtime/test_wrappers/test_strncmp.c

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+int main(int argc, char *argv[]) {
+
+  char    buf[1024];
+  ssize_t i;
+  if ((i = read(0, buf, sizeof(buf) - 1)) < 24) return 0;
+  buf[i] = 0;
+  if (buf[0] != 'A') return 0;
+  if (buf[1] != 'B') return 0;
+  if (buf[2] != 'C') return 0;
+  if (buf[3] != 'D') return 0;
+  if (memcmp(buf + 4, "1234", 4) || memcmp(buf + 8, "EFGH", 4)) return 0;
+  if (strncmp(buf + 12, "AAAA", 4) == 0){
+    printf("HIT!\n");
+  } else {
+    printf("NOT HIT!\n");
+  }
+
+  return 0;
+
+}