C++ version for GCC development

[Xi Ruoyao]

On Thu, 2022-03-03 at 22:07 -0500, Abdullah Siddiqui via Gcc-help wrote:
> Hello Jonathan.
> 
> Thank you for the detailed clarification.
> 
> > At what point did the GCC developers give up C++98 and start using C++11?
> 
> 
> For GCC 11. This is stated at https://gcc.gnu.org/install/prerequisites.html
> 
> 
> Are you referring to these lines:
> 
> ISO C++11 compiler
> > Necessary to bootstrap GCC.
> 
>  Versions of GCC prior to 11 also allow bootstrapping with an ISO C++98
> > compiler,.....
> 
> 
> I thought bootstrapping and compilation are two separate things. In this
> context, are bootstrapping and compilation the same i.e. GCC is a compiler
> and the ISO C++11 compiler is being used to compile GCC?

In theory, compiling GCC with --disable-bootstrap may have a *more*
strict restriction on host compiler than bootstrapping (--enable-
bootstrap is the default building a native compiler).  It's because with
--disable-bootstrap the entire GCC will be built with the host compiler,
but with --enable-bootstrap only stage 1 is built with the host
compiler, and stage 2 is built with stage 1.  In stage 1 some optional
features (Go or D compilers, etc) are not enabled.

But in practice I don't know.  Maybe it's possible to build GCC 11 with
GCC 4.8 and --disable-bootstrap but I've not tried.  I don't think it's
really rational to spend an hour testing this in 2022.

> The exceptions are some tests which have .c extensions but get
> > compiled as both C and C++, when we want to test that both language
> > front-ends pass the test.
> 
> 
> Are you referring to files in the testsuite folders
> (example: gcc/testsuite/g++.dg/lto/pr65302_1.C)?

Files in g++.dg are purely C++.  Please note ".C" (with a capital
letter) is not same as ".c".

For example, gcc/testsuite/c-c++-common/pr100785.c is compiled as both C
and C++ during the testing process of GCC.
> 
-- 
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University