[M3devel] gcc vs. g++ in config files?

[Jay K]

Sorry, this merits more discussion.

 - There are at least three ways compilers chose between C and C++.

 invocation name: gcc vs. g++, lowercase cc vs. uppercase CC
  I think clang vs. clang++.
 Visual C++ only has one invocation: cl
 Source file extension: .c vs. .cpp, .cxx, .cc, .C, etc.This is very common with Visual C++.
 Command line switches:
  gcc -x c++ 
  clang -x C++
  cl -Tc means next source file is C
   -TC means all are C
   -Tp means next is C++
   -TP means all are C++
We'd have to read up on others.

 One of the combinations implemented by gcc is deprecated by clang.
 I think clang++ foo.c. And, actually g++ foo.c (Apple installs clang as gcc).
 So I switched to use -x c++.

 "cpp" is ambiguous between C preprocessor and C++.
 "cxx" is often therefore used to indicate C++. x is a rotated +.
 We could have config files specify SYSTEM_CC and SYSTEM_CXX.
 And we could have functions compile_c and compile_cxx. 
 We could have builder c_source("foo") probe for foo.c, and foo.cpp, maybe
 others, error if there are multiple, and chose compile_c vs. compile_cxx.
 Or compile_c could chose based on the extension.

 In any case, makes changes to the C backend path, and in the llvm binding/backend
 directories should be easy. We don't *have* to change the meanings everywhere
 to effect them. I do not actually intend to rewrite all of our little bits
 of C using C++ specific features. But the LLVM stuff uses C++ and the C backend
 imho ought to.

 - Jay




From: jay.krell at cornell.edu
To: m3devel at elegosoft.com
Date: Tue, 1 Sep 2015 16:28:10 +0000
Subject: [M3devel] gcc vs. g++ in config files?




I suggest we replace "gcc" with "g++".In all the config files (and in the bootstrap archives).And similar for Sun CC, and Visual C++ use -TP.

rationale: It will likely cleanup our LLVM stuff, which currently uses a custom Makefile and drops derived files into the src directory.  It will ease/allow using C++ exception handling in the C backend.  I've been using g++ for months/years on Darwin. counter-rationale: Not all C code is valid C++, and sometimes the meanings are different. I converted the coverage code only recently.

 - Jay

 		 	   		  

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