[all-commits] [llvm/llvm-project] 796d26: [flang] Fix ISO_Fortran_binding.h to work better w...

[Pete Steinfeld via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 796d26a37d70374e41766df659700a826dc62e34
      https://github.com/llvm/llvm-project/commit/796d26a37d70374e41766df659700a826dc62e34
  Author: Pete Steinfeld <47540744+psteinfeld at users.noreply.github.com>
  Date:   2024-02-26 (Mon, 26 Feb 2024)

  Changed paths:
    M flang/include/flang/ISO_Fortran_binding.h
    A flang/test/Integration/iso-fortran-binding.cpp

  Log Message:
  -----------
  [flang] Fix ISO_Fortran_binding.h to work better with C++ code (#82556)

[flang] Fix ISO_Fortran_binding.h to work better with C++ code

This stems from working on LANL's "dopey" project --
https://github.com/lanl/dopey.

That project contains C++ code which includes the header file
"ISO_Fortran_binding.h". The dopey code wraps that include with an
'extern "C"' clause since the standard (18.5.1, paragraph 1) says that
the file" shall contain C structure definitions, typedef declarations,
...". But the clang++ compiler emits error messages objecting to the
fact that ISO_Fortran_binding.h contains templates.

This change fixes that by preceding the problematic code in
ISO_Fortran_binding.h with language linkage clauses that specify that
they contain C++ code rather than C code.

In the accompanying test, I needed to account for the fact that some
people build the compiler by doing a `make check-flang`. In this case,
the clang compiler which is required by the test will not be built.

Here's an example of a C++ program that shows the problem:
```
  extern "C" {
  #include "ISO_Fortran_binding.h"
  }
  int main() {
    return 0;
  }
```



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