Hi Iain, Thank again for the detailed reply, understood now.
Shivam On Sun, 3 Apr 2022 at 12:23 PM, Iain Sandoe <i...@sandoe.co.uk> wrote: > Hi Shivam, > > > On 2 Apr 2022, at 17:48, Shivam Gupta <shivam98....@gmail.com> wrote: > > > > > May I ask why we need to specify --with-gxx-libcxx-include-dir= at > compile/configure time of GCC? > > The libc++ headers are not part of a base system install (on Darwin they > are part of either Xcode or Command Line Tools installations). On other > platforms, they will be an optional install. It seems unhelpful to enable > an option that will not work (without knowing where to find the headers, > -stdlib=libc++ cannot work). > > For GCC, the default is to use -stdlib=libstdc++, and that is part of the > compiler’s install so that it can be located without extra configuration, > and it does not require the -stdlib option to work. > > > While in clang equivalent, -stdlib= doesn't require so. > > libc++ is the default for clang and is part of the standard compiler > distribution (so it can be located without additional configuration). > > OTOH, I believe that you will find that to make -stdlib=libstdc++ work > will generally require some cmake values to point to the GCC installation > (On macOS/Darwin there is a default that points to the old apple-gcc-4.2.1 > installation [for Darwin11-16], but that is not necessarily the GCC version > you would be using there, either). > > In summary, since neither compiler “knows” where to find the other, some > configuration is required in the general case to find the non-native C++ > runtime. > > Iain > >
