Hi Martin, In short yes, it is special behavior but I'm not sure that it is intended. Each target can opt in to *not* have -isystem implicitly wrap headers in extern C construct. Arm target does not do anything special and thus inherit that default behavior of implicit extern C, except when targeting uclinux systems. It seems from [1] that it is this way for legacy reason.
[1] https://gcc.gnu.org/ml/gcc-patches/2012-06/msg01151.html Best regards, Thomas On 24 January 2018 at 17:02, Kaul, Martin <martin.k...@leuze.com> wrote: > Hi, > > given the following code: > > -- isystem_test.cpp ------------- > #include < isystem_test.h> > > bool dummy_function( void ) > { > return false; > } > ----------------------------------------- > > -- isystem_test.h ------------------ > template <class _CS_cT> > class allocator > { > }; > ----------------------------------------- > > and g++ version: arm-eabi-g++.exe (Linaro GCC 7.2-2017.11) > > 1. compiling with "arm-eabi-g++ -I . -g -c isystem_test.cpp" > --> OK > > 2. compiling with " arm-eabi-g++ -isystem . -g -c isystem_test.cpp " > --> output error: > In file included from isystem_test.cpp:3:0: > ./isystem_test.h:3:1: error: template with C linkage > template <class _CS_cT> > ^~~~~~~~ > > It seams that the option -isystem changes the include of isystems_test.h > into a C include, i.e. the header content seems to be handled as C-Code > > Same error behavior with arm-eabi Linaro GCC 6.4-2017.11, Linaro GCC > 6.3-2017.05 > > ----------------- > Testing the same with the mingw msys g++ compiler outputs no error: > g++.exe (Rev2, Built by MSYS2 project) 7.2.0 > Copyright (C) 2017 Free Software Foundation, Inc. > This is free software; see the source for copying conditions. There is NO > warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. > --------------- > Also no errors for: > arm-linux-gnueabihf-g++.exe (Linaro GCC 6.3-2017.05) > --------------- > > Is there a special behavior for arm-eabi g++ compiler? > > Best regards > Martin Kaul > > _______________________________________________ > linaro-toolchain mailing list > linaro-toolchain@lists.linaro.org > https://lists.linaro.org/mailman/listinfo/linaro-toolchain > _______________________________________________ linaro-toolchain mailing list linaro-toolchain@lists.linaro.org https://lists.linaro.org/mailman/listinfo/linaro-toolchain
