Update __VERSION__ to remove the hardcoded 4.2.1 version

[sylvestre.ledru]

Summary

Just like in https://reviews.llvm.org/D56803
for -dumpversion

[xbolva00]

Btw, what about this code

// Currently claim to be compatible with GCC 4.2.1-5621, but only if we're
// not compiling for MSVC compatibility
Builder.defineMacro("__GNUC_MINOR__", "2");
Builder.defineMacro("__GNUC_PATCHLEVEL__", "1");
Builder.defineMacro("__GNUC__", "4");

?

[sylvestre.ledru]

update of the release notes

[sylvestre.ledru]

In D63048#1535222, @xbolva00 wrote:

Btw, what about this code

// Currently claim to be compatible with GCC 4.2.1-5621, but only if we're
// not compiling for MSVC compatibility
Builder.defineMacro("__GNUC_MINOR__", "2");
Builder.defineMacro("__GNUC_PATCHLEVEL__", "1");
Builder.defineMacro("__GNUC__", "4");

?

Dunno, what do you think @rnk ?

[hubert.reinterpretcast]

docs/ReleaseNotes.rst

85

Use code font for __VERSION__.

lib/Frontend/InitPreprocessor.cpp

610

s/as/for/; s/gcc/GCC/;
Add a period to the end of the sentence.

611

s/returns/return/; s/clang/Clang/;

[sylvestre.ledru]

Fix the typo (thanks hubert)

[hubert.reinterpretcast]

docs/ReleaseNotes.rst

85

I think this needs double backquotes on both sides.

[sylvestre.ledru]

fix rst syntax

[lebedev.ri]

lib/Frontend/InitPreprocessor.cpp

613

So how does the entire __VERSION__ macro looks like now?

[sylvestre.ledru]

lib/Frontend/InitPreprocessor.cpp

613

#define __VERSION__ "9.0.0 Compatible Clang 9.0.0 (trunk 362877)"

instead of

#define __VERSION__ "4.2.1 Compatible Clang 9.0.0 (trunk 362877)"

clang -dM -E -xc - < /dev/null

to see it

[rnk]

Personally, I think it's safe to do this. I believe this "4.2.1" compat thing was something Apple added as part of their switch from GCC, and then llvm-gcc, over to Clang, and I think most of the code they care about probably doesn't rely on __VERSION__ anymore. In any case, we should let @dexonsmith know.

As an alternative, maybe we should just stop defining the __VERSION__ macro. It's ambiguous. What is it the version of? The compiler, or the standard library? What gives the compiler the right to take some identifier, even in the implementer's namespace, and use it without putting it in their namespace by adding clang or GNUC to it? We already define __clang_version__, which has the same information.

lib/Frontend/InitPreprocessor.cpp

613

If we're going to make this change, I don't think we need to say $VER Compatible Clang $VER, we can just say Clang $VER (trunk $REVISION), so this can be simplified to getClangFullCPPVersion(). For a vendor like Apple, it will become Apple Clang N.M.Q, which is probably fine. @dexonsmith

[sylvestre.ledru]

I will wait for @dexonsmith 's opinion

[sylvestre.ledru]

@dexonsmith ping?

[dexonsmith]

In D63048#1558806, @sylvestre.ledru wrote:

@dexonsmith ping?

I think I'd be a little more comfortable dropping __VERSION__ entirely. There's already a way to access the clang version, and anyone with code that relies on "4.2.1" can just add a -D__VERSION__=... to their build rules to keep existing behaviour.

FWIW, I feel similarly about -dumpversion (better to remove it than change it).

[lebedev.ri]

In D63048#1559880, @dexonsmith wrote:

In D63048#1558806, @sylvestre.ledru wrote:

@dexonsmith ping?

...

FWIW, I feel similarly about -dumpversion (better to remove it than change it).

What does CMake use to detect compiler (well, clang) version?

[lebedev.ri]

In D63048#1559894, @lebedev.ri wrote:

In D63048#1559880, @dexonsmith wrote:

In D63048#1558806, @sylvestre.ledru wrote:

@dexonsmith ping?

...

FWIW, I feel similarly about -dumpversion (better to remove it than change it).

What does CMake use to detect compiler (well, clang) version?

Spoke too soon, clearly not that.

[sylvestre.ledru]

@rnk how do you feel about removing both? I can take care of that if you want

[rnk]

I'd be in favor of removing them.

[sylvestre.ledru]

Actually, not sure it is a good idea to remove them: https://reviews.llvm.org/D64062#1566460

[sylvestre.ledru]

Implement the change (just update VERSION)

[rnk]

lgtm

[xbolva00]

Some ICC behaviour..

icc -dumpversion
19.0.3.199

printf("%d %d %s", GNUC, GNUC_MINOR, VERSION);
./a.out
7 4 Intel(R) C++ gcc 7.4 mode

Should we bump GNUC, GNUC_MINOR too?

[xbolva00]

https://bugs.llvm.org/show_bug.cgi?id=42817

[rnk]

In D63048#1605050, @xbolva00 wrote:

Should we bump GNUC, GNUC_MINOR too?

We discussed this two weeks ago:
http://lists.llvm.org/pipermail/cfe-dev/2019-July/062890.html
It's unlikely that we will make any policy change before 9.0.

docs/LanguageExtensions.rst

 option for a warning and returns true if that is a valid warning option.
 
 .. code-block:: c++
 
   #if __has_warning("-Wformat")
   ...
   #endif
 
+.. _languageextensions-builtin-macros:
+
 Builtin Macros
 ==============
 
 ``__BASE_FILE__``
   Defined to a string that contains the name of the main input file passed to
   Clang.
 
 ``__FILE_NAME__``

docs/ReleaseNotes.rst

 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 - ...
 
 Non-comprehensive list of changes in this release
 -------------------------------------------------
 
+- The ``__VERSION__`` macro has been updated.
+  Previously this macro contained the string '4.2.1 Compatible' to achieve
+  compatibility with GCC 4.2.1, but that should no longer be necessary.
+  However, to retrieve Clang's version, please favor the one of the macro
+  defined in :ref:`clang namespaced version macros <languageextensions-builtin-macros>`.
+
 - ...
 
 
 New Compiler Flags
 ------------------
 
 - ...
 
 Deprecated Compiler Flags
 -------------------------
 
 The following options are deprecated and ignored. They will be removed in
 future versions of Clang.
 
 - ...
 
 Modified Compiler Flags
 -----------------------
 
 - ``clang -dumpversion`` now returns the version of Clang itself.
 
 - ...
 
 New Pragmas in Clang
 --------------------
 
 - ...
 
 Attribute Changes in Clang

lib/Frontend/InitPreprocessor.cpp

#undef TOSTR2
   Builder.defineMacro("__OPENCL_MEMORY_SCOPE_WORK_GROUP", "1");
   Builder.defineMacro("__OPENCL_MEMORY_SCOPE_DEVICE", "2");
   Builder.defineMacro("__OPENCL_MEMORY_SCOPE_ALL_SVM_DEVICES", "3");
   Builder.defineMacro("__OPENCL_MEMORY_SCOPE_SUB_GROUP", "4");
 
   // Support for #pragma redefine_extname (Sun compatibility)
   Builder.defineMacro("__PRAGMA_REDEFINE_EXTNAME", "1");
 
-  // As sad as it is, enough software depends on the __VERSION__ for version
-  // checks that it is necessary to report 4.2.1 (the base GCC version we claim
-  // compatibility with) first.
-  Builder.defineMacro("__VERSION__", "\"4.2.1 Compatible " +
+  // Previously this macro was set to a string aiming to achieve compatibility
+  // with GCC 4.2.1. Now, just return the full Clang version
+  Builder.defineMacro("__VERSION__", "\"" +
                       Twine(getClangFullCPPVersion()) + "\"");
 
   // Initialize language-specific preprocessor defines.
 
   // Standard conforming mode?
   if (!LangOpts.GNUMode && !LangOpts.MSVCCompat)
     Builder.defineMacro("__STRICT_ANSI__");
 
   if (!LangOpts.MSVCCompat && LangOpts.CPlusPlus11)
     Builder.defineMacro("__GXX_EXPERIMENTAL_CXX0X__");
 
   if (LangOpts.ObjC) {

test/Preprocessor/init.c

 // SPARC:#define __UINT_LEAST16_TYPE__ unsigned short
 // SPARC:#define __UINT_LEAST32_MAX__ 4294967295U
 // SPARC:#define __UINT_LEAST32_TYPE__ unsigned int
 // SPARC:#define __UINT_LEAST64_MAX__ 18446744073709551615ULL
 // SPARC:#define __UINT_LEAST64_TYPE__ long long unsigned int
 // SPARC:#define __UINT_LEAST8_MAX__ 255
 // SPARC:#define __UINT_LEAST8_TYPE__ unsigned char
 // SPARC:#define __USER_LABEL_PREFIX__
-// SPARC:#define __VERSION__ "4.2.1 Compatible{{.*}}
+// SPARC:#define __VERSION__ "Clang{{.*}}
 // SPARC:#define __WCHAR_MAX__ 2147483647
 // SPARC:#define __WCHAR_TYPE__ int
 // SPARC:#define __WCHAR_WIDTH__ 32
 // SPARC:#define __WINT_TYPE__ int
 // SPARC:#define __WINT_WIDTH__ 32
 // SPARC:#define __sparc 1
 // SPARC:#define __sparc__ 1
 // SPARC:#define __sparcv8 1

 // X86_64-CLOUDABI:#define __UINT_LEAST64_TYPE__ long unsigned int
 // X86_64-CLOUDABI:#define __UINT_LEAST8_FMTX__ "hhX"
 // X86_64-CLOUDABI:#define __UINT_LEAST8_FMTo__ "hho"
 // X86_64-CLOUDABI:#define __UINT_LEAST8_FMTu__ "hhu"
 // X86_64-CLOUDABI:#define __UINT_LEAST8_FMTx__ "hhx"
 // X86_64-CLOUDABI:#define __UINT_LEAST8_MAX__ 255
 // X86_64-CLOUDABI:#define __UINT_LEAST8_TYPE__ unsigned char
 // X86_64-CLOUDABI:#define __USER_LABEL_PREFIX__
-// X86_64-CLOUDABI:#define __VERSION__ "4.2.1 Compatible{{.*}}
+// X86_64-CLOUDABI:#define __VERSION__ "Clang{{.*}}
 // X86_64-CLOUDABI:#define __WCHAR_MAX__ 2147483647
 // X86_64-CLOUDABI:#define __WCHAR_TYPE__ int
 // X86_64-CLOUDABI:#define __WCHAR_WIDTH__ 32
 // X86_64-CLOUDABI:#define __WINT_MAX__ 2147483647
 // X86_64-CLOUDABI:#define __WINT_TYPE__ int
 // X86_64-CLOUDABI:#define __WINT_WIDTH__ 32
 // X86_64-CLOUDABI:#define __amd64 1
 // X86_64-CLOUDABI:#define __amd64__ 1