Add support for the CompCert C Compiler

* Add preliminary support for the CompCert C Compiler

The intention is to use this with the picolibc, so some GCC flags are
automatically filtered. Since CompCert uses GCC is for linking, those
GCC-linker flags which are used by picolibc, are automatically prefixed
with '-WUl', so that they're passed to GCC.

Squashed commit of the following:

commit 4e0ad66dca9de301d2e41e74aea4142afbd1da7d
Author: Sebastian Meyer <meyer@absint.com>
Date:   Mon Aug 31 14:20:39 2020 +0200

    remove '-fall' from default arguments, also filter -ftls-model=.*

commit 41afa3ccc62ae72824eb319cb8b34b7e6693cb67
Author: Sebastian Meyer <meyer@absint.com>
Date:   Mon Aug 31 14:13:55 2020 +0200

    use regex for filtering ccomp args

commit d68d242d0ad22f8bf53923ce849da9b86b696a75
Author: Sebastian Meyer <meyer@absint.com>
Date:   Mon Aug 31 13:54:36 2020 +0200

    filter some gcc arguments

commit 982a01756266bddbbd211c54e8dbfa2f43dec38f
Author: Sebastian Meyer <meyer@absint.com>
Date:   Fri Aug 28 15:03:14 2020 +0200

    fix ccomp meson configuration

commit dce0bea00b1caa094b1ed0c6c77cf6c12f0f58d9
Author: Sebastian Meyer <meyer@absint.com>
Date:   Thu Aug 27 13:02:19 2020 +0200

    add CompCert to meson (does not fully work, yet)

* remove unused import and s/cls/self/

fixes the two obvious LGTM warnings

* CompCert: Do not ignore unsupported GCC flags

Some are safe to ignore, however, as per
https://github.com/mesonbuild/meson/pull/7674, they should not be
ignored by meson itself. Instead the meson.build should take care to
select only those which are actually supported by the compiler.

* remove unused variable

* Only add arguments once.

* Apply suggestions from code review

Co-authored-by: Dylan Baker <dylan@pnwbakers.com>

* Remove erroneous ' ' from '-o {}'.format()

As noticed by @dcbaker

* added release note snippet for compcert

* properly split parameters

As suggested by @dcbaker, these parameters should be properly split into multiple strings.

Co-authored-by: Dylan Baker <dylan@pnwbakers.com>

* Update add_compcert_compiler.md

Added a sentence about the state of the implementation (experimental); use proper markdown

* properly separate arguments

Co-authored-by: Dylan Baker <dylan@pnwbakers.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index 13ca1d4..5cfa06c 100644
--- a/mesonbuild/compilers/c.py
+++ b/mesonbuild/compilers/c.py
@@ -22,6 +22,7 @@ from .c_function_attributes import C_FUNC_ATTRIBUTES
 from .mixins.clike import CLikeCompiler
 from .mixins.ccrx import CcrxCompiler
 from .mixins.xc16 import Xc16Compiler
+from .mixins.compcert import CompCertCompiler
 from .mixins.c2000 import C2000Compiler
 from .mixins.arm import ArmCompiler, ArmclangCompiler
 from .mixins.visualstudio import MSVCCompiler, ClangClCompiler
@@ -554,6 +555,36 @@ class Xc16CCompiler(Xc16Compiler, CCompiler):
             path = '.'
         return ['-I' + path]
 
+class CompCertCCompiler(CompCertCompiler, CCompiler):
+    def __init__(self, exelist, version, for_machine: MachineChoice,
+                 is_cross, info: 'MachineInfo', exe_wrapper=None, **kwargs):
+        CCompiler.__init__(self, exelist, version, for_machine, is_cross,
+                           info, exe_wrapper, **kwargs)
+        CompCertCompiler.__init__(self)
+
+    def get_options(self):
+        opts = CCompiler.get_options(self)
+        opts.update({'c_std': coredata.UserComboOption('C language standard to use',
+                                                       ['none', 'c89', 'c99'],
+                                                       'none')})
+        return opts
+
+    def get_option_compile_args(self, options):
+        return []
+
+    def get_no_optimization_args(self):
+        return ['-O0']
+
+    def get_output_args(self, target):
+        return ['-o{}'.format(target)]
+
+    def get_werror_args(self):
+        return ['-Werror']
+
+    def get_include_args(self, path, is_system):
+        if path == '':
+            path = '.'
+        return ['-I' + path]
 
 class C2000CCompiler(C2000Compiler, CCompiler):
     def __init__(self, exelist, version, for_machine: MachineChoice,