Compiling gcc trunk under cygwin

[David Wohlferd <dw at LimeGreenSocks dot com>]

Until recently, I've been able to build gcc under cygwin just fine. But 
(relatively) recent checkins (232454 &  232071) are causing problems.  
I've been trying to track down what to do about them, but crawling thru 
the depths of makefiles, sed scripts, etc is proving difficult for this 
long-time Windows programmer.  But I do have some clues.

The problems all seem to revolve around __GXX_WEAK__.

I notice that cygwin's current (and experimental 5.2.0) builds of gcc 
don't define __GXX_WEAK__.  After reading this 
(https://cygwin.com/ml/cygwin/2010-04/msg00281.html), that makes sense.  
And that's fine by me, I don't need it anyway.

But during the building of gcc, the xgcc that gets built *does* define 
it.  And with these new changes, that leads to errors like this:

../src/c++11/.libs/libc++11convenience.a(cow-stdexcept.o): In function 
`_txnal_cow_string_C1_for_exceptions(void*, char const*, void*)':
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:236:(.text$_Z35_txnal_cow_string_C1_for_exceptionsPvPKcS_+0x2c): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol 
`_ITM_RU1'
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:248:(.text$_Z35_txnal_cow_string_C1_for_exceptionsPvPKcS_+0x39): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol 
`transaction clone for operator
new[](unsigned long)'
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:267:(.text$_Z35_txnal_cow_string_C1_for_exceptionsPvPKcS_+0x5d): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol 
`_ITM_memcpyRtWn'
../src/c++11/.libs/libc++11convenience.a(cow-stdexcept.o): In function 
`txnal_read_ptr':
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:278:(.text$_Z23_txnal_cow_string_c_strPKv+0x1): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol 
`_ITM_RU8'
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:278:(.text$_Z23_txnal_sso_string_c_strPKv+0x1): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol 
`_ITM_RU8'
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:278:(.text$_Z20_txnal_cow_string_D1Pv+0x5): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol 
`_ITM_RU8'
../src/c++11/.libs/libc++11convenience.a(cow-stdexcept.o): In function 
`_txnal_cow_string_D1(void*)':
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:324:(.text$_Z20_txnal_cow_string_D1Pv+0x1e): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol 
`_ITM_addUserCommitAction'
../src/c++11/.libs/libc++11convenience.a(cow-stdexcept.o): In function 
`transaction clone for std::logic_error::logic_error(char const*)':
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:408:(.text$_ZGTtNSt11logic_errorC1EPKc+0x2e): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol 
`_ITM_memcpyRnWt'
../src/c++11/.libs/libc++11convenience.a(cow-stdexcept.o): In function 
`transaction clone for 
std::logic_error::logic_error(std::__cxx11::basic_string<char, 
std::char_traits<char>, std::allocator<char> > const&)':
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:408:(.text$_ZGTtNSt11logic_errorC1ERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x2e): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol
`_ITM_memcpyRnWt'
../src/c++11/.libs/libc++11convenience.a(cow-stdexcept.o): In function 
`txnal_read_ptr':
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:278:(.text$_ZGTtNSt11logic_errorC1ERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x36): 
relocation truncated to fit: R_X86_64_PC32 against undefined symbol
`_ITM_RU8'
../src/c++11/.libs/libc++11convenience.a(cow-stdexcept.o): In function 
`transaction clone for std::logic_error::~logic_error()':
/cygdrive/c/cygwin64/src/gcc-trunk/libstdc++-v3/src/c++11/cow-stdexcept.cc:408:(.text$_ZGTtNSt11logic_errorD0Ev+0x1a): 
additional relocation overflows omitted from the output

I can fix the errors and get my build working again by:
a) adding "#define __GXX_WEAK__ 0" to the top of cow-stdexcept.cc
b) commenting out the undef and define of MAKE_DECL_ONE_ONLY in cygming.h

But there's got to be a better way.

Is there some configure option I'm supposed to be using when building 
gcc for cygwin?  How else could your 5.2.0 not be defining 
__GXX_WEAK__?  Looking at the configure options in gcc -v isn't showing 
me anything that looks like a solution.

dw

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