Fix build failures due to missing JEMALLOC_CXX_THROW macro (facebook#…

…5053)

Summary:
JEMALLOC_CXX_THROW is not defined for earlier versions of jemalloc (e.g. 3.6), causing builds to fail on some platforms. Fixing it. Closes facebook#4869
Pull Request resolved: facebook#5053

Differential Revision: D14390034

Pulled By: sagar0

fbshipit-source-id: b2b7a03cd377201ef385eb521f65bae85c558055

HISTORY.md

@@ -1,12 +1,14 @@
 # Rocksdb Change Log
 ## 5.18.4 (3/3/2020)
 * Various fixes for ARM64 support (#6250)
+* Fix JEMALLOC_CXX_THROW macro missing from older Jemalloc versions, causing build failures on some platforms.
 
 ## 5.18.3 (2/11/2019)
 ### Bug Fixes
 * Fix possible LSM corruption when both range deletions and subcompactions are used. The symptom of this corruption is L1+ files overlapping in the user key space.
 
 ## 5.18.2 (01/31/2019)
+
 ### Public API Change
 * Change time resolution in FileOperationInfo.
 * Deleting Blob files also go through SStFileManager.

port/jemalloc_helper.h

@@ -12,6 +12,10 @@
 #include <jemalloc/jemalloc.h>
 #endif
 
+#ifndef JEMALLOC_CXX_THROW
+#define JEMALLOC_CXX_THROW
+#endif
+
 // Declare non-standard jemalloc APIs as weak symbols. We can null-check these
 // symbols to detect whether jemalloc is linked with the binary.
 extern "C" void* mallocx(size_t, int) __attribute__((__weak__));