compilers: Use keyword only arguments for compiler interfaces

Because we need to inherit them in some cases, and python's
keyword-or-positional arguments make this really painful, especially
with inheritance. They do this in two ways:

1) If you want to intercept the arguments you need to check for both a
   keyword and a positional argument, because you could get either. Then
   you need to make sure that you only pass one of those down to the
   next layer.

2) After you do that, if the layer below you decides to do the same
   thing, but uses the other form (you used keyword by the lower level
   uses positional or vice versa), then you'll get a TypeError since two
   layers down got the argument as both a positional and a keyword.

All of this is bad. Fortunately python 3.x provides a mechanism to solve
this, keyword only arguments. These arguments cannot be based
positionally, the interpreter will give us an error in that case.

I have made a best effort to do this correctly, and I've verified it
with GCC, Clang, ICC, and MSVC, but there are other compilers like Arm
and Elbrus that I don't have access to.

1 files changed, 53 insertions, 34 deletions

diff --git a/mesonbuild/compilers/c.py b/mesonbuild/compilers/c.py
index b57001a..4d3b2a2 100644
--- a/mesonbuild/compilers/c.py
+++ b/mesonbuild/compilers/c.py
@@ -209,7 +209,9 @@ class CCompiler(Compiler):
     def _get_search_dirs(self, env):
         extra_args = ['--print-search-dirs']
         stdo = None
-        with self._build_wrapper('', env, extra_args, None, 'compile', True) as p:
+        with self._build_wrapper('', env, extra_args=extra_args,
+                                 dependencies=None, mode='compile',
+                                 want_output=True) as p:
             stdo = p.stdo
         return stdo
 
@@ -361,13 +363,14 @@ class CCompiler(Compiler):
         code = 'int main(int argc, char **argv) { int class=0; return class; }\n'
         return self.sanity_check_impl(work_dir, environment, 'sanitycheckc.c', code)
 
-    def check_header(self, hname, prefix, env, extra_args=None, dependencies=None):
+    def check_header(self, hname, prefix, env, *, extra_args=None, dependencies=None):
         fargs = {'prefix': prefix, 'header': hname}
         code = '''{prefix}
         #include <{header}>'''
-        return self.compiles(code.format(**fargs), env, extra_args, dependencies)
+        return self.compiles(code.format(**fargs), env, extra_args=extra_args,
+                             dependencies=dependencies)
 
-    def has_header(self, hname, prefix, env, extra_args=None, dependencies=None):
+    def has_header(self, hname, prefix, env, *, extra_args=None, dependencies=None):
         fargs = {'prefix': prefix, 'header': hname}
         code = '''{prefix}
         #ifdef __has_include
@@ -377,10 +380,10 @@ class CCompiler(Compiler):
         #else
          #include <{header}>
         #endif'''
-        return self.compiles(code.format(**fargs), env, extra_args,
-                             dependencies, 'preprocess')
+        return self.compiles(code.format(**fargs), env, extra_args=extra_args,
+                             dependencies=dependencies, mode='preprocess')
 
-    def has_header_symbol(self, hname, symbol, prefix, env, extra_args=None, dependencies=None):
+    def has_header_symbol(self, hname, symbol, prefix, env, *, extra_args=None, dependencies=None):
         fargs = {'prefix': prefix, 'header': hname, 'symbol': symbol}
         t = '''{prefix}
         #include <{header}>
@@ -390,7 +393,8 @@ class CCompiler(Compiler):
                 {symbol};
             #endif
         }}'''
-        return self.compiles(t.format(**fargs), env, extra_args, dependencies)
+        return self.compiles(t.format(**fargs), env, extra_args=extra_args,
+                             dependencies=dependencies)
 
     def _get_compiler_check_args(self, env, extra_args, dependencies, mode='compile'):
         if callable(extra_args):
@@ -437,7 +441,7 @@ class CCompiler(Compiler):
         args += extra_args
         return args
 
-    def compiles(self, code, env, extra_args=None, dependencies=None, mode='compile'):
+    def compiles(self, code, env, *, extra_args=None, dependencies=None, mode='compile'):
         with self._build_wrapper(code, env, extra_args, dependencies, mode) as p:
             return p.returncode == 0
 
@@ -445,10 +449,11 @@ class CCompiler(Compiler):
         args = self._get_compiler_check_args(env, extra_args, dependencies, mode)
         return self.compile(code, args, mode, want_output=want_output)
 
-    def links(self, code, env, extra_args=None, dependencies=None):
-        return self.compiles(code, env, extra_args, dependencies, mode='link')
+    def links(self, code, env, *, extra_args=None, dependencies=None):
+        return self.compiles(code, env, extra_args=extra_args,
+                             dependencies=dependencies, mode='link')
 
-    def run(self, code, env, extra_args=None, dependencies=None):
+    def run(self, code, env, *, extra_args=None, dependencies=None):
         if self.is_cross and self.exe_wrapper is None:
             raise CrossNoRunException('Can not run test applications in this cross environment.')
         with self._build_wrapper(code, env, extra_args, dependencies, mode='link', want_output=True) as p:
@@ -478,7 +483,8 @@ class CCompiler(Compiler):
         t = '''#include <stdio.h>
         {prefix}
         int main() {{ static int a[1-2*!({expression})]; a[0]=0; return 0; }}'''
-        return self.compiles(t.format(**fargs), env, extra_args, dependencies)
+        return self.compiles(t.format(**fargs), env, extra_args=extra_args,
+                             dependencies=dependencies)
 
     def cross_compute_int(self, expression, low, high, guess, prefix, env, extra_args, dependencies):
         # Try user's guess first
@@ -528,7 +534,7 @@ class CCompiler(Compiler):
 
         return low
 
-    def compute_int(self, expression, low, high, guess, prefix, env, extra_args=None, dependencies=None):
+    def compute_int(self, expression, low, high, guess, prefix, env, *, extra_args=None, dependencies=None):
         if extra_args is None:
             extra_args = []
         if self.is_cross:
@@ -540,14 +546,15 @@ class CCompiler(Compiler):
             printf("%ld\\n", (long)({expression}));
             return 0;
         }};'''
-        res = self.run(t.format(**fargs), env, extra_args, dependencies)
+        res = self.run(t.format(**fargs), env, extra_args=extra_args,
+                       dependencies=dependencies)
         if not res.compiled:
             return -1
         if res.returncode != 0:
             raise EnvironmentException('Could not run compute_int test binary.')
         return int(res.stdout)
 
-    def cross_sizeof(self, typename, prefix, env, extra_args=None, dependencies=None):
+    def cross_sizeof(self, typename, prefix, env, *, extra_args=None, dependencies=None):
         if extra_args is None:
             extra_args = []
         fargs = {'prefix': prefix, 'type': typename}
@@ -556,30 +563,33 @@ class CCompiler(Compiler):
         int main(int argc, char **argv) {{
             {type} something;
         }}'''
-        if not self.compiles(t.format(**fargs), env, extra_args, dependencies):
+        if not self.compiles(t.format(**fargs), env, extra_args=extra_args,
+                             dependencies=dependencies):
             return -1
         return self.cross_compute_int('sizeof(%s)' % typename, None, None, None, prefix, env, extra_args, dependencies)
 
-    def sizeof(self, typename, prefix, env, extra_args=None, dependencies=None):
+    def sizeof(self, typename, prefix, env, *, extra_args=None, dependencies=None):
         if extra_args is None:
             extra_args = []
         fargs = {'prefix': prefix, 'type': typename}
         if self.is_cross:
-            return self.cross_sizeof(typename, prefix, env, extra_args, dependencies)
+            return self.cross_sizeof(typename, prefix, env, extra_args=extra_args,
+                                     dependencies=dependencies)
         t = '''#include<stdio.h>
         {prefix}
         int main(int argc, char **argv) {{
             printf("%ld\\n", (long)(sizeof({type})));
             return 0;
         }};'''
-        res = self.run(t.format(**fargs), env, extra_args, dependencies)
+        res = self.run(t.format(**fargs), env, extra_args=extra_args,
+                       dependencies=dependencies)
         if not res.compiled:
             return -1
         if res.returncode != 0:
             raise EnvironmentException('Could not run sizeof test binary.')
         return int(res.stdout)
 
-    def cross_alignment(self, typename, prefix, env, extra_args=None, dependencies=None):
+    def cross_alignment(self, typename, prefix, env, *, extra_args=None, dependencies=None):
         if extra_args is None:
             extra_args = []
         fargs = {'prefix': prefix, 'type': typename}
@@ -588,7 +598,8 @@ class CCompiler(Compiler):
         int main(int argc, char **argv) {{
             {type} something;
         }}'''
-        if not self.compiles(t.format(**fargs), env, extra_args, dependencies):
+        if not self.compiles(t.format(**fargs), env, extra_args=extra_args,
+                             dependencies=dependencies):
             return -1
         t = '''#include <stddef.h>
         {prefix}
@@ -598,11 +609,12 @@ class CCompiler(Compiler):
         }};'''
         return self.cross_compute_int('offsetof(struct tmp, target)', None, None, None, t.format(**fargs), env, extra_args, dependencies)
 
-    def alignment(self, typename, prefix, env, extra_args=None, dependencies=None):
+    def alignment(self, typename, prefix, env, *, extra_args=None, dependencies=None):
         if extra_args is None:
             extra_args = []
         if self.is_cross:
-            return self.cross_alignment(typename, prefix, env, extra_args, dependencies)
+            return self.cross_alignment(typename, prefix, env, extra_args=extra_args,
+                                        dependencies=dependencies)
         fargs = {'prefix': prefix, 'type': typename}
         t = '''#include <stdio.h>
         #include <stddef.h>
@@ -615,7 +627,8 @@ class CCompiler(Compiler):
             printf("%d", (int)offsetof(struct tmp, target));
             return 0;
         }}'''
-        res = self.run(t.format(**fargs), env, extra_args, dependencies)
+        res = self.run(t.format(**fargs), env, extra_args=extra_args,
+                       dependencies=dependencies)
         if not res.compiled:
             raise EnvironmentException('Could not compile alignment test.')
         if res.returncode != 0:
@@ -659,7 +672,7 @@ class CCompiler(Compiler):
         int main(int argc, char *argv[]) {{
             printf ("{fmt}", {cast} {f}());
         }}'''.format(**fargs)
-        res = self.run(code, env, extra_args, dependencies)
+        res = self.run(code, env, extra_args=extra_args, dependencies=dependencies)
         if not res.compiled:
             m = 'Could not get return value of {}()'
             raise EnvironmentException(m.format(fname))
@@ -728,7 +741,7 @@ class CCompiler(Compiler):
         }}'''
         return head, main
 
-    def has_function(self, funcname, prefix, env, extra_args=None, dependencies=None):
+    def has_function(self, funcname, prefix, env, *, extra_args=None, dependencies=None):
         """
         First, this function looks for the symbol in the default libraries
         provided by the compiler (stdlib + a few others usually). If that
@@ -776,7 +789,8 @@ class CCompiler(Compiler):
             head, main = self._no_prototype_templ()
         templ = head + stubs_fail + main
 
-        if self.links(templ.format(**fargs), env, extra_args, dependencies):
+        if self.links(templ.format(**fargs), env, extra_args=extra_args,
+                      dependencies=dependencies):
             return True
 
         # MSVC does not have compiler __builtin_-s.
@@ -809,9 +823,10 @@ class CCompiler(Compiler):
             #endif
         #endif
         }}'''
-        return self.links(t.format(**fargs), env, extra_args, dependencies)
+        return self.links(t.format(**fargs), env, extra_args=extra_args,
+                          dependencies=dependencies)
 
-    def has_members(self, typename, membernames, prefix, env, extra_args=None, dependencies=None):
+    def has_members(self, typename, membernames, prefix, env, *, extra_args=None, dependencies=None):
         if extra_args is None:
             extra_args = []
         fargs = {'prefix': prefix, 'type': typename, 'name': 'foo'}
@@ -825,7 +840,8 @@ class CCompiler(Compiler):
             {type} {name};
             {members}
         }};'''
-        return self.compiles(t.format(**fargs), env, extra_args, dependencies)
+        return self.compiles(t.format(**fargs), env, extra_args=extra_args,
+                             dependencies=dependencies)
 
     def has_type(self, typename, prefix, env, extra_args, dependencies=None):
         fargs = {'prefix': prefix, 'type': typename}
@@ -833,7 +849,8 @@ class CCompiler(Compiler):
         void bar() {{
             sizeof({type});
         }};'''
-        return self.compiles(t.format(**fargs), env, extra_args, dependencies)
+        return self.compiles(t.format(**fargs), env, extra_args=extra_args,
+                             dependencies=dependencies)
 
     def symbols_have_underscore_prefix(self, env):
         '''
@@ -1221,11 +1238,13 @@ class ElbrusCCompiler(GnuCCompiler, ElbrusCompiler):
 
     # Elbrus C compiler does not have lchmod, but there is only linker warning, not compiler error.
     # So we should explicitly fail at this case.
-    def has_function(self, funcname, prefix, env, extra_args=None, dependencies=None):
+    def has_function(self, funcname, prefix, env, *, extra_args=None, dependencies=None):
         if funcname == 'lchmod':
             return False
         else:
-            return super().has_function(funcname, prefix, env, extra_args, dependencies)
+            return super().has_function(funcname, prefix, env,
+                                        extra_args=extra_args,
+                                        dependencies=dependencies)
 
 
 class IntelCCompiler(IntelCompiler, CCompiler):