[scudo] Fix an edge case in the secondary allocator

Summary:
s/CHECK_LT/CHECK_LE/ in the secondary allocator, as under certain circumstances
Ptr + Size can be equal to MapEnd. This edge case was not found by the current
tests, so those were extended to be able to catch that.

Reviewers: kcc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D25101

llvm-svn: 282913
diff --git a/compiler-rt/lib/scudo/scudo_utils.cpp b/compiler-rt/lib/scudo/scudo_utils.cpp
index f45569e..9e6a351 100644
--- a/compiler-rt/lib/scudo/scudo_utils.cpp
+++ b/compiler-rt/lib/scudo/scudo_utils.cpp
@@ -34,8 +34,8 @@
 
 FORMAT(1, 2)
 void NORETURN dieWithMessage(const char *Format, ...) {
-  // Our messages are tiny, 128 characters is more than enough.
-  char Message[128];
+  // Our messages are tiny, 256 characters is more than enough.
+  char Message[256];
   va_list Args;
   va_start(Args, Format);
   __sanitizer::VSNPrintf(Message, sizeof(Message), Format, Args);