[ASan] Support {f}puts(NULL) on Darwin

On Darwin, the man page states that "both fputs() and puts() print
`(null)' if str is NULL."

rdar://48227136

Reviewed By: Lekensteyn

Differential Revision: https://reviews.llvm.org/D64773

llvm-svn: 366342

Author: yln

compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc

@@ -1241,7 +1241,8 @@ INTERCEPTOR_WITH_SUFFIX(int, fputs, char *s, void *file) {
   // libc file streams can call user-supplied functions, see fopencookie.
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, fputs, s, file);
-  COMMON_INTERCEPTOR_READ_RANGE(ctx, s, REAL(strlen)(s) + 1);
+  if (!SANITIZER_MAC || s)
+    COMMON_INTERCEPTOR_READ_RANGE(ctx, s, REAL(strlen)(s) + 1);
   return REAL(fputs)(s, file);
 }
 #define INIT_FPUTS COMMON_INTERCEPT_FUNCTION(fputs)
@@ -1254,7 +1255,8 @@ INTERCEPTOR(int, puts, char *s) {
   // libc file streams can call user-supplied functions, see fopencookie.
   void *ctx;
   COMMON_INTERCEPTOR_ENTER(ctx, puts, s);
-  COMMON_INTERCEPTOR_READ_RANGE(ctx, s, REAL(strlen)(s) + 1);
+  if (!SANITIZER_MAC || s)
+    COMMON_INTERCEPTOR_READ_RANGE(ctx, s, REAL(strlen)(s) + 1);
   return REAL(puts)(s);
 }
 #define INIT_PUTS COMMON_INTERCEPT_FUNCTION(puts)

compiler-rt/test/sanitizer_common/TestCases/Darwin/fputs_puts_null.cc

@@ -0,0 +1,16 @@
+// On Darwin, the man page states that "both fputs() and puts() print `(null)'
+// if str is NULL."
+//
+// RUN: %clangxx -g %s -o %t && %run %t | FileCheck %s
+// CHECK: {{^\(null\)---\(null\)$}}
+
+#include <assert.h>
+#include <stdio.h>
+
+int main(void) {
+  assert(fputs(NULL, stdout) >= 0);
+  fputs("---", stdout);
+  assert(puts(NULL) >= 0);
+
+  return 0;
+}