[asan] Fix an OS X startup crash when an empty section is present

On OS X, when the main instrumented binary contains a custom section with zero length, ASan will crash (assert failure) early in the initialization.

Reviewed at http://reviews.llvm.org/D10944

llvm-svn: 241474

2 files changed, 13 insertions, 0 deletions

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_posix.cc b/compiler-rt/lib/sanitizer_common/sanitizer_posix.cc
index de4b8d1406e..5754c9029ed 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_posix.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_posix.cc
@@ -270,6 +270,7 @@ bool MemoryRangeIsAvailable(uptr range_start, uptr range_end) {
   while (proc_maps.Next(&start, &end,
                         /*offset*/0, /*filename*/0, /*filename_size*/0,
                         /*protection*/0)) {
+    if (start == end) continue;  // Empty range.
     CHECK_NE(0, end);
     if (!IntervalsAreSeparate(start, end - 1, range_start, range_end))
       return false;
diff --git a/compiler-rt/test/asan/TestCases/Darwin/empty-section.cc b/compiler-rt/test/asan/TestCases/Darwin/empty-section.cc
new file mode 100644
index 00000000000..5b006b54548
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/Darwin/empty-section.cc
@@ -0,0 +1,12 @@
+// Regression test with an empty (length = 0) custom section.
+
+// RUN: %clangxx_asan -g -O0 %s -c -o %t.o
+// RUN: %clangxx_asan -g -O0 %t.o -o %t -sectcreate mysegment mysection /dev/null
+// RUN: %run %t 2>&1 | FileCheck %s
+
+#include <stdio.h>
+
+int main() {
+  printf("Hello, world!\n");
+  // CHECK: Hello, world!
+}