As of 2020-08-01, OpenBSD's system zlib is 1.2.3 which doesn't
have gzoffset(). However we can get away with this by making
gzfilebuf::approxOffset() always return zero.
Avoids need to specify the 3rd-party dir, in the standard/fgmeta
layout of source directories, and accept more combinations of path,
when the user specifies a value.
It seems that clang++ headers #include <version>, which found simgear/version
because we need to put singear/ in include path for some code to compile.
making the build between Simgear and Flightgear consistent.
- Fix an issue with lib/lib64 path between CentOS/RedHat distributions
and Debian derived distributions.
When CMAKE_BUILD_TYPE is Debug and we are compiling with GCC, add the
following options to CMAKE_C_FLAGS and CMAKE_CXX_FLAGS:
-O0 -fno-omit-frame-pointer -fno-inline
Ditto for Clang, except that -fno-inline-functions is used instead of
-fno-inline.
cf. thread starting at
https://sourceforge.net/p/flightgear/mailman/message/36295412/
Explicitly enable the CMP0067 policy to have try_compile use the correct
C/C++ standard flags; otherwise, CMake will default to not honoring those,
causing the C/C++ checks to be compiled with no standard flags and SimGear
to be compiled with them. This causes errors if we try to detect a new
prototype which is only present in C++14 and above).
Indent the test code in a nicer way and shorten it, taking advantage of
this guarantee from the C++ standard:
If control reaches the end of main without encountering a return
statement, the effect is that of executing return 0.
-> no need for "#include <cstdlib>" nor for "return EXIT_SUCCESS".
Define HAVE_WORKING_STD_REGEX if, and only if <regex> is usable.
Normally, <regex> should be available and working in any compliant C++11
implementation, however at least g++ 4.8[1] lies about its C++11
compliance: its <regex> is utterly unusable, see [2] and [3] for
details.
[1] Which appears to be (precisely 4.8.5) the version shipped in
CentOS 7, and used on FlightGear's current Jenkins installation.
[2] https://stackoverflow.com/a/12665408/4756009
[3] https://sourceforge.net/p/flightgear/mailman/message/36170781/
