Fleshed out and added a bunch of useful stuff, notably 'check_func()',

'try_cpp()', 'search_cpp()', and 'check_header()'.  This is enough that
the base config is actually useful for implementing a real config
command, specifically one for mxDateTime.

Lib/distutils/command/config.py

@@ -13,7 +13,7 @@ this header file lives".
 
 __revision__ = "$Id$"
 
-import os, string
+import sys, os, string, re
 from distutils.core import Command
 from distutils.errors import DistutilsExecError
 
@@ -40,6 +40,11 @@ class config (Command):
          "external C libraries to link with"),
         ('library-dirs=', 'L',
          "directories to search for external C libraries"),
+
+        ('noisy', None,
+         "show every action (compile, link, run, ...) taken"),
+        ('dump-source', None,
+         "dump generated source files before attempting to compile them"),
         ]
 
 
@@ -55,6 +60,14 @@ class config (Command):
         self.libraries = None
         self.library_dirs = None
 
+        # maximal output for now
+        self.noisy = 1
+        self.dump_source = 1
+
+        # list of temporary files generated along-the-way that we have
+        # to clean at some point
+        self.temp_files = []
+
     def finalize_options (self):
         pass
 
@@ -75,7 +88,7 @@ class config (Command):
         from distutils.ccompiler import CCompiler, new_compiler
         if not isinstance(self.compiler, CCompiler):
             self.compiler = new_compiler (compiler=self.compiler,
-                                          verbose=self.verbose, # for now
+                                          verbose=self.noisy,
                                           dry_run=self.dry_run,
                                           force=1)
             if self.include_dirs:
@@ -86,25 +99,48 @@ class config (Command):
                 self.compiler.set_library_dirs(self.library_dirs)
 
 
-    def _gen_temp_sourcefile (self, body, lang):
+    def _gen_temp_sourcefile (self, body, headers, lang):
         filename = "_configtest" + LANG_EXT[lang]
         file = open(filename, "w")
+        if headers:
+            for header in headers:
+                file.write("#include <%s>\n" % header)
+            file.write("\n")
         file.write(body)
+        if body[-1] != "\n":
+            file.write("\n")
         file.close()
         return filename
 
-    def _compile (self, body, lang):
-        src = self._gen_temp_sourcefile(body, lang)
-        (obj,) = self.compiler.compile([src])
+    def _preprocess (self, body, headers, lang):
+        src = self._gen_temp_sourcefile(body, headers, lang)
+        out = "_configtest.i"
+        self.temp_files.extend([src, out])
+        self.compiler.preprocess(src, out)
+        return (src, out)
+
+    def _compile (self, body, headers, lang):
+        src = self._gen_temp_sourcefile(body, headers, lang)
+        if self.dump_source:
+            dump_file(src, "compiling '%s':" % src)
+        (obj,) = self.compiler.object_filenames([src])
+        self.temp_files.extend([src, obj])
+        self.compiler.compile([src])
         return (src, obj)
 
-    def _link (self, body, lang):
-        (src, obj) = self._compile(body, lang)
-        exe = os.path.splitext(os.path.basename(src))[0]
-        self.compiler.link_executable([obj], exe)
-        return (src, obj, exe)
+    def _link (self, body, headers, libraries, library_dirs, lang):
+        (src, obj) = self._compile(body, headers, lang)
+        prog = os.path.splitext(os.path.basename(src))[0] 
+        self.temp_files.append(prog)    # XXX should be prog + exe_ext
+        self.compiler.link_executable([obj], prog,
+                                      libraries=libraries,
+                                      library_dirs=library_dirs)
+        return (src, obj, prog)
 
     def _clean (self, *filenames):
+        if not filenames:
+            filenames = self.temp_files
+            self.temp_files = []
         self.announce("removing: " + string.join(filenames))
         for filename in filenames:
             try:
@@ -113,10 +149,6 @@ class config (Command):
                 pass
 
 
-    # XXX no 'try_cpp()' or 'search_cpp()' since the CCompiler interface
-    # does not provide access to the preprocessor.  This is an oversight
-    # that should be fixed.
-
     # XXX these ignore the dry-run flag: what to do, what to do? even if
     # you want a dry-run build, you still need some sort of configuration
     # info.  My inclination is to make it up to the real config command to
@@ -125,56 +157,168 @@ class config (Command):
     # return either true or false from all the 'try' methods, neither of
     # which is correct.
 
-    def try_compile (self, body, lang="c"):
-        """Try to compile a source file that consists of the text in 'body'
-        (a multi-line string).  Return true on success, false
-        otherwise.
+    # XXX need access to the header search path and maybe default macros.
+
+    def try_cpp (self, body=None, headers=None, lang="c"):
+        """Construct a source file from 'body' (a string containing lines
+        of C/C++ code) and 'headers' (a list of header files to include)
+        and run it through the preprocessor.  Return true if the
+        preprocessor succeeded, false if there were any errors.
+        ('body' probably isn't of much use, but what the heck.)
         """
         from distutils.ccompiler import CompileError
         self._check_compiler()
+        ok = 1
         try:
-            (src, obj) = self._compile(body, lang)
+            self._preprocess(body, headers, lang)
+        except CompileError:
+            ok = 0
+
+        self._clean()
+        return ok
+
+    def search_cpp (self, pattern, body=None, headers=None, lang="c"):
+        """Construct a source file (just like 'try_cpp()'), run it through
+        the preprocessor, and return true if any line of the output matches
+        'pattern'.  'pattern' should either be a compiled regex object or a
+        string containing a regex.  If both 'body' and 'headers' are None,
+        preprocesses an empty file -- which can be useful to determine the
+        symbols the preprocessor and compiler set by default.
+        """
+
+        self._check_compiler()
+        (src, out) = self._preprocess(body, headers, lang)
+
+        if type(pattern) is StringType:
+            pattern = re.compile(pattern)
+
+        file = open(out)
+        match = 0
+        while 1:
+            line = file.readline()
+            if line == '':
+                break
+            if pattern.search(pattern):
+                match = 1
+                break
+
+        file.close()
+        self._clean()
+        return match
+
+    def try_compile (self, body, headers=None, lang="c"):
+        """Try to compile a source file built from 'body' and 'headers'.
+        Return true on success, false otherwise.
+        """
+        from distutils.ccompiler import CompileError
+        self._check_compiler()
+        try:
+            self._compile(body, headers, lang)
             ok = 1
         except CompileError:
             ok = 0
 
         self.announce(ok and "success!" or "failure.")
-        self._clean(src, obj)
+        self._clean()
         return ok
 
-    def try_link (self, body, lang="c"):
-        """Try to compile and link a source file (to an executable) that
-        consists of the text in 'body' (a multi-line string).  Return true
-        on success, false otherwise.
+    def try_link (self,
+                  body, headers=None,
+                  libraries=None, library_dirs=None,
+                  lang="c"):
+        """Try to compile and link a source file, built from 'body' and
+        'headers', to executable form.  Return true on success, false
+        otherwise.
         """
         from distutils.ccompiler import CompileError, LinkError
         self._check_compiler()
         try:
-            (src, obj, exe) = self._link(body, lang)
+            self._link(body, headers, libraries, library_dirs, lang)
             ok = 1
         except (CompileError, LinkError):
             ok = 0
 
         self.announce(ok and "success!" or "failure.")
-        self._clean(src, obj, exe)
+        self._clean()
         return ok
             
-    def try_run (self, body, lang="c"):
-        """Try to compile, link to an executable, and run a program that
-        consists of the text in 'body'.  Return true on success, false
+    def try_run (self,
+                 body, headers=None, 
+                 libraries=None, library_dirs=None,
+                 lang="c"):
+        """Try to compile, link to an executable, and run a program
+        built from 'body' and 'headers'.  Return true on success, false
         otherwise.
         """
         from distutils.ccompiler import CompileError, LinkError
         self._check_compiler()
         try:
-            (src, obj, exe) = self._link(body, lang)
+            self._link(body, headers, libraries, library_dirs, lang)
             self.spawn([exe])
             ok = 1
         except (CompileError, LinkError, DistutilsExecError):
             ok = 0
 
         self.announce(ok and "success!" or "failure.")
-        self._clean(src, obj, exe)
+        self._clean()
         return ok
 
+
+    # -- High-level methods --------------------------------------------
+    # (these are the ones that are actually likely to be useful
+    # when implementing a real-world config command!)
+
+    def check_func (self, func, headers=None,
+                    libraries=None, library_dirs=None,
+                    decl=0, call=0):
+
+        """Determine if function 'func' is available by constructing a
+        source file that refers to 'func', and compiles and links it.
+        If everything succeeds, returns true; otherwise returns false.
+
+        The constructed source file starts out by including the header
+        files listed in 'headers'.  If 'decl' is true, it then declares
+        'func' (as "int func()"); you probably shouldn't supply 'headers'
+        and set 'decl' true in the same call, or you might get errors about
+        a conflicting declarations for 'func'.  Finally, the constructed
+        'main()' function either references 'func' or (if 'call' is true)
+        calls it.  'libraries' and 'library_dirs' are used when
+        linking.
+        """
+
+        self._check_compiler()
+        body = []
+        if decl:
+            body.append("int %s ();" % func)
+        body.append("int main () {")
+        if call:
+            body.append("  %s();" % func)
+        else:
+            body.append("  %s;" % func)
+        body.append("}")
+        body = string.join(body, "\n") + "\n"
+
+        return self.try_link(body, headers, libraries, library_dirs)
+
+    # check_func ()
+
+    def check_header (self, header, lang="c"):
+        """Determine if the system header file named by 'header_file'
+        exists and can be found by the preprocessor; return true if so,
+        false otherwise.
+        """
+        return self.try_cpp(headers=[header])
+
+
 # class config
+
+
+def dump_file (filename, head=None):
+    if head is None:
+        print filename + ":"
+    else:
+        print head
+
+    file = open(filename)
+    sys.stdout.write(file.read())
+    file.close()