The former appended the necessary switch to enable C++11 to the CXXFLAGS
whereas AX_CXX_COMPILE_STDCXX appends it to CXX which has the benefit
that all C++ sources are compiled using the same C++ standard. Therefore
it is no longer necessary to manually hardcode '-std=c++11' anywhere
like we did in the Ruby bindings linker command and assures that the
compilation of them is done with C++11 support as well.
This fixes bug #795
Provide SR_ARG_OPT_CHECK, a generalized variant of SRG_ARG_OPT_PKG
that can be used with custom check commands. Implement the latter
in terms of SR_ARG_OPT_CHECK.
Put the extra libraries into SR_EXTRA_LIBS instead of LIBS.
Create an SR_CHECK_LIBS macro to make that easy. Substitute
SR_EXTRA_LIBS into libsigrok.pc, too.
Place a copy of ax_cxx_compile_stdcxx_11.m4 from the Autoconf
macro archive into our private m4/ directory. This is cleaner
than trying to parse M4 file versions etc. Plus, the macro is
now always available.
Introduce the SR_CHECK_COMPILE_FLAGS macro and use it to check
for additional compiler flags. Put the accepted flags into the
separate substitution variable SR_EXTRA_CFLAGS.
With this and the preceding changes, bug #578 should now be fixed.
Use the SR_ARG_ENABLE_WARNINGS macro to configure and check for
the availability of compiler warning flags. Maintain separate
sets of warning flags for C and C++.
The configure option --enable-warnings=[min|max|fatal|no] can
be used to set the compiler warning level for all languages.
The default level is "max".
Place custom Autoconf macros which other sigrok modules may
re-use into a separate file m4/sigrok.m4. Also, introduce new
macros for defining the package and library versions, and for
gathering compiler warning flags.
Marvin Schmidt
Daniel Elstner
Uwe Hermann