Hello,
It seems to me that here is a logical error: https://github.com/bitcoin/bitcoin/blob/07ce278455757fb46dab95fb9b97a3f6b1b84faf/configure.ac#L47-L53
All code below "hopes" that CXXFLAGS_overridden is no when CXXFLAGS is empty. Right?
In my opinion the variable name a bit confusing. I read entire configure.ac file several times and still not sure if I understood it correctly. What do you think about "can_override_cxxflags" name?
This variable indicates that CXXFLAGS has been overridden, like
./configure CXXFLAGS=-O2, then CXXFLAGS_overridden=yes
./configure, then CXXFLAGS_overridden=no
@ken2812221 Yes. I thought so too. But take a look for example at this condition: https://github.com/bitcoin/bitcoin/blob/eeae4711f338ef2621f2f0295b974dee846cc36f/configure.ac#L245-L249
Do we need clean the CXXFLAGS here? Isn't the CXXFLAGS empty here (due to CXXFLAGS_overridden is no)?
Default CXXFLAGS is not empty, It is -g -O2. We don't use this flag when we are debugging, so we clear it.
Previously we're convinced that CXXFLAGS is empty. As I can see there is no code, before 245 line that sets CXXFLAGS. For CXXFLAGS="-g -O2" the CXXFLAGS_overridden would be yes. Why do we need clear CXXFLAGS for CXXFLAGS_overridden=no? It seems I'm confused again :)
Aha! Got it:
+ AC_MSG_WARN("CXXFLAGS=$CXXFLAGS")
AC_PROG_CXX
+ AC_MSG_ERROR("CXXFLAGS=$CXXFLAGS")
+ configure: WARNING: "CXXFLAGS="
checking for g++... g++
checking whether the C++ compiler works... yes
checking for C++ compiler default output file name... a.out
checking for suffix of executables...
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C++ compiler... yes
checking whether g++ accepts -g... yes
checking for style of include used by make... GNU
checking dependency style of g++... gcc3
+ configure: error: "CXXFLAGS=-g -O2"
Thank you for your patience and clarification :)