Fix fdatasync() feature detection in opensource build.

The CMake feature-detection code used check_symbol_exists(), which
invokes the C compiler. However, some glibc versions don't expose the
fdatasync() declaration when compiled with -std=c11, but do expose it
when compiled with -std=c++11. This most likely comes down to how
_POSIX_SOURCE is defined -- it needs to be >= 201112L for <unistd.h> to
expose fdatasync().

This CL switches to check_cxx_symbol_exists(), which uses the C++
compiler. Asides from fixing the problem above, this is the right thing
to do, because we use <unistd.h> in env_posix.cc, which is compiled with
the C++ compiler.

This CL also fixes a previously introduced inconsistency, where the
macro indicating the fdatasync() feature detection result was referred
to as HAVE_FDATASYNC and HAVE_FUNC_FDATASYNC. The former appears to be
used in other libraries, so this CL switches all our references to
HAVE_FDATASYNC.

Fixes https://github.com/google/leveldb/issues/629

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=228392612
This commit is contained in:
costan
2019-01-08 13:49:13 -08:00
committed by Victor Costan
parent af7abf06ea
commit b70493ca85
2 changed files with 10 additions and 5 deletions

View File

@@ -6,9 +6,9 @@
#define STORAGE_LEVELDB_PORT_PORT_CONFIG_H_
// Define to 1 if you have a definition for fdatasync() in <unistd.h>.
#if !defined(HAVE_FUNC_FDATASYNC)
#cmakedefine01 HAVE_FUNC_FDATASYNC
#endif // !defined(HAVE_FUNC_FDATASYNC)
#if !defined(HAVE_FDATASYNC)
#cmakedefine01 HAVE_FDATASYNC
#endif // !defined(HAVE_FDATASYNC)
// Define to 1 if you have Google CRC32C.
#if !defined(HAVE_CRC32C)