Re: [PATCH] X86: Provide a CTOR for stringop_algs [PR100246].

[Iain Sandoe <iain@sandoe.co.uk>]

Hi Richard,

> On 5 Jul 2021, at 11:50, Richard Biener via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> 
> On Sun, Jul 4, 2021 at 10:04 PM Iain Sandoe <iain@sandoe.co.uk> wrote:

>> Several older compilers fail to build modern GCC because of missing
>> or incomplete C++11 support.
>> 
>> (although the PR mentions clang, specifically, this has also been reported
>> for some GCC versions within the range that should be able to bootstrap
>> GCC)
>> 
>> There are several possible solutions proposed in the PR, this one seems
>> the least invasive.
>> 
>> The header is pulled into the gcov code that builds with C, so we have to
>> make the CTOR conditional on C++.
>> 
>> tested on Darwin12 with xcode-6, bootstrapped on x86_64-darwin and linux.
>> OK for master / GCC-11?
> 
> Hmm, what is specifically built with a C compiler?  gcov.c not, I think.

any C compilation that includes tm.h

well, libgcc2 fails too on a quick check here -  but ISTR there was something in
libgcov and I checked with Martin that it was intentionally compiled with C compiler.

> Instead of commenting the CTOR, does it work to comment the whole stringop_algs
> type?

I don’t think that will work because it’s in a header that’s transitively included by tm.h
which is then included loads of places.

>  Also it seems on trunk this CTOR is no more?

The addition of the CTOR is the fix for the C++ compile fail in the PR, the conditional is
only there because the same header is compiled by C and C++.

thanks
Iain
> 
>> thanks
>> Iain
>> 
>> Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>
>> 
>> PR bootstrap/100246 - [11/12 Regression] GCC will not bootstrap with clang 3.4/3.5 [xcode 5/6, Darwin 12/13]
>> 
>>        PR bootstrap/100246
>> 
>> gcc/ChangeLog:
>> 
>>        * config/i386/i386.h (struct stringop_algs): Define a CTOR for
>>        this type.
>> ---
>> gcc/config/i386/i386.h | 5 +++++
>> 1 file changed, 5 insertions(+)
>> 
>> diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
>> index 6e0340a4b60..84151156999 100644
>> --- a/gcc/config/i386/i386.h
>> +++ b/gcc/config/i386/i386.h
>> @@ -73,6 +73,11 @@ struct stringop_algs
>> {
>>   const enum stringop_alg unknown_size;
>>   const struct stringop_strategy {
>> +#ifdef __cplusplus
>> +    stringop_strategy(int _max = -1, enum stringop_alg _alg = libcall,
>> +                     int _noalign = false)
>> +      : max (_max), alg (_alg), noalign (_noalign) {}
>> +#endif
>>     const int max;
>>     const enum stringop_alg alg;
>>     int noalign;
>> --
>> 2.24.1