Compilation failure on macOS inside GCC

[Ben Boeckel]

Hi,

I am seeing the following build failure when built as part of GCC (namely https://github.com/iains/gcc-13-branch) on macOS with Xcode 14.2:

```

depbase=`echo isl_test_cpp17.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
        g++ -std=c++11 -DHAVE_CONFIG_H   -I. -I../../src/isl -I../../src/isl/include -Iinclude/ -I/Users/ben.boeckel/code/ci-utilities/src/build/gcc/build/gmp/../../src/gmp -I/Users/ben.boeckel/code/ci-utilities/src
/build/gcc/build/./gmp   -g -MT isl_test_cpp17.o -MD -MP -MF $depbase.Tpo -c -o isl_test_cpp17.o ../../src/isl/isl_test_cpp17.cc &&\
        mv -f $depbase.Tpo $depbase.Po
In file included from ../../src/isl/isl_test_cpp17.cc:20:                                                                                                                                                              
../../src/isl/isl_test_cpp17-generic.cc:25:10: error: no matching constructor for initialization of 'isl::id'
        isl::id id(ctx, "S", s);                                                                          
                ^  ~~~~~~~~~~~                                                                            
../../src/isl/include/isl/cpp.h:10994:5: note: candidate constructor not viable: requires 2 arguments, but 3 were provided
id::id(isl::ctx ctx, const std::string &str)                                                              
    ^                                                                                                      
../../src/isl/include/isl/cpp.h:10976:5: note: candidate constructor not viable: requires single argument 'ptr', but 3 arguments were provided
id::id(__isl_take isl_id *ptr)  
    ^                                                                                                                                                                                                                  
../../src/isl/include/isl/cpp.h:10982:5: note: candidate constructor not viable: requires single argument 'obj', but 3 arguments were provided
id::id(const id &obj)
    ^                                                                                                                                                                                                                  
../../src/isl/include/isl/cpp.h:10979:5: note: candidate constructor not viable: requires 0 arguments, but 3 were provided
id::id()
    ^

```

I've tried `export HAVE_CXX17=0`, but it still shows up. What is causing `-std=c++11` to be passed explicitly to the C++17 tests? I see `config.log` has:

```

configure:9259: checking whether g++ -std=c++11 supports C++17 features by default
configure:10054: g++ -std=c++11 -c -g  conftest.cpp >&5
conftest.cpp:312:2: error: "This is not a C++14 compiler"
#error "This is not a C++14 compiler"
 ^
conftest.cpp:432:2: error: "This is not a C++17 compiler"
#error "This is not a C++17 compiler"
 ^

```

So it *shouldn't* have C++17 assumed anyways (though I wonder why this test has `-std=c++11`… Some investigation there seems to point to `gcc`'s `config.log` having `CXX='g++ -std=c++11`. However, it seems that `isl` should be a bit more consistent with its own C++17 flag management.

Thanks,

--Ben

[Sven Verdoolaege]

On Mon, Aug 28, 2023 at 06:37:00AM -0700, 'Ben Boeckel' via isl Development wrote:
> ```

> configure:9259: checking whether g++ -std=c++11 supports C++17 features by
> default
> configure:10054: g++ -std=c++11 -c -g conftest.cpp >&5
> conftest.cpp:312:2: error: "This is not a C++14 compiler"
> #error "This is not a C++14 compiler"
> ^
> conftest.cpp:432:2: error: "This is not a C++17 compiler"
> #error "This is not a C++17 compiler"
> ^
> ```

If your compiler doesn't support C++17, then isl_test_cpp17
shouldn't get built. I can only imagine something went wrong
in the generation of Makefile.
What version of isl are you trying to comile?
Send config.log, config.status and Makefile.

skimo

[Ben Boeckel]

I'm linking the `isl` 0.26 extracted source into `gcc` and bootstrapping
it.

> Send config.log, config.status and Makefile.

Attached.

--Ben

[Sven Verdoolaege]

On Mon, Aug 28, 2023 at 06:37:00AM -0700, 'Ben Boeckel' via isl Development wrote:
> ```

> configure:9259: checking whether g++ -std=c++11 supports C++17 features by
> default
> configure:10054: g++ -std=c++11 -c -g conftest.cpp >&5
> conftest.cpp:312:2: error: "This is not a C++14 compiler"
> #error "This is not a C++14 compiler"
> ^
> conftest.cpp:432:2: error: "This is not a C++17 compiler"
> #error "This is not a C++17 compiler"
> ^
> ```
>
> So it *shouldn't* have C++17 assumed anyways

Actually, no. This is just the first attempt.
It does later find that "g++ -std=c++11 -std=gnu++17" works.
Your Makefile also has

CXX = g++ -std=c++11 -std=gnu++17

> ```

> depbase=`echo isl_test_cpp17.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
> g++ -std=c++11 -DHAVE_CONFIG_H -I. -I../../src/isl

But "-std=gnu++17" somehow got dropped here.
Are you perhaps overriding CXX when running make?
If so, don't.

skimo

[Ben Boeckel]

On Mon, Aug 28, 2023 at 23:52:25 +0200, Sven Verdoolaege wrote:
> But "-std=gnu++17" somehow got dropped here.
> Are you perhaps overriding CXX when running make?
> If so, don't.

I'm not, but maybe GCC is… I'll see if anyone has issues on the GCC
side.

--Ben