# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1486571071 -3600
# Node ID c34d7d187b2c7aff1cd6f6974d88e0b4c995b481
# Parent  aa11ebd14c79eac3a5bcda5c18d8593f0aaa665d
Introduced a warnings mechanism to support invocation-related messages.
Added a help message and handled missing command line arguments better.

diff -r aa11ebd14c79 -r c34d7d187b2c importer.py
--- a/importer.py	Wed Feb 08 16:20:27 2017 +0100
+++ b/importer.py	Wed Feb 08 17:24:31 2017 +0100
@@ -35,7 +35,7 @@
 
     special_attributes = ("__args__", "__file__", "__fn__", "__name__", "__parent__")
 
-    def __init__(self, path, cache=None, verbose=False):
+    def __init__(self, path, cache=None, verbose=False, warnings=None):
 
         """
         Initialise the importer with the given search 'path' - a list of
@@ -46,11 +46,15 @@
 
         The optional 'verbose' parameter causes output concerning the activities
         of the object to be produced if set to a true value (not the default).
+
+        The optional 'warnings' parameter may indicate classes of warnings to be
+        produced.
         """
 
         self.path = path
         self.cache = cache
         self.verbose = verbose
+        self.warnings = warnings
 
         # Module importing queue, required modules, removed modules and active
         # modules in the final program.
@@ -116,6 +120,12 @@
 
         self.make_cache()
 
+    def give_warning(self, name):
+
+        "Return whether the indicated warning 'name' should be given."
+
+        return self.warnings and (name in self.warnings or "all" in self.warnings)
+
     def make_cache(self):
 
         "Make a cache directory if it does not already exist."
diff -r aa11ebd14c79 -r c34d7d187b2c lplc
--- a/lplc	Wed Feb 08 16:20:27 2017 +0100
+++ b/lplc	Wed Feb 08 17:24:31 2017 +0100
@@ -43,12 +43,59 @@
     stdout, stderr = cmd.communicate()
     return cmd.wait()
 
+def start_arg_list(l, arg, prefix, needed):
+
+    """
+    Add to 'l' any value given as part of 'arg' having the given option
+    'prefix'. The 'needed' number of values is provided in case no value is
+    found.
+
+    Return 'l' and 'needed' decremented by 1 together in a tuple.
+    """
+
+    s = arg[len(prefix):].strip()
+    if s:
+        l.append(s)
+        return l, needed - 1
+    else:
+        return l, needed
+
 # Main program.
 
 if __name__ == "__main__":
+    basename = split(sys.argv[0])[-1]
     args = sys.argv[1:]
     path = libdirs
 
+    if "--help" in args or not args:
+        print >>sys.stderr, """\
+Usage: %s [ <options> ] <filename>
+
+Compile the program whose principal file is given in place of <filename>.
+The following options may be specified:
+
+-c   Only partially compile the program; do not attempt to build or link it
+-g   Generate debugging information for the built executable
+-q   Silence messages produced when building an executable
+-r   Reset (discard) cached program information; inspect the whole program again
+-tb  Provide a traceback for any internal errors (development only)
+-v   Report compiler activities in a verbose fashion (development only)
+
+Some options may be followed by values, either immediately after the option
+(without any space between) or in the arguments that follow them:
+
+-o   Indicate the output executable name
+-W   Show warnings on the topics indicated
+
+Currently, the following warnings are supported:
+
+all     Show all possible warnings
+
+args    Show invocations where a callable may be involved that cannot accept the
+        arguments provided
+""" % basename
+        sys.exit(1)
+
     # Determine the options and arguments.
 
     debug = False
@@ -57,6 +104,7 @@
     reset = False
     traceback = False
     verbose = False
+    warnings = []
 
     filenames = []
     outputs = []
@@ -64,6 +112,7 @@
     # Obtain program filenames by default.
 
     l = filenames
+    needed = None
 
     for arg in args:
         if arg == "-c": make = False
@@ -71,20 +120,21 @@
         elif arg == "-q": make_verbose = False
         elif arg == "-r": reset = True
         elif arg == "-tb": traceback = True
-        elif arg == "-o": l = outputs
+        elif arg.startswith("-o"): l, needed = start_arg_list(outputs, arg, "-o", 1)
         elif arg == "-v": verbose = True
+        elif arg.startswith("-W"): l, needed = start_arg_list(warnings, arg, "-W", 1)
         else:
             l.append(arg)
+            if needed:
+                needed -= 1
 
-            # Revert to collecting program filenames after obtaining the output
-            # executable filename.
-
-            if l is outputs: l = filenames
+        if needed == 0:
+            l = filenames
 
     # Obtain the program filename.
 
-    if len(filenames) > 1:
-        print >>sys.stderr, "Only one main program file can be specified."
+    if len(filenames) != 1:
+        print >>sys.stderr, "One main program file must be specified."
         sys.exit(1)
 
     filename = abspath(filenames[0])
@@ -92,6 +142,9 @@
 
     # Obtain the output filename.
 
+    if outputs and not make:
+        print >>sys.stderr, "Output specified but building disabled."
+
     output = outputs and outputs[0] or "_main"
 
     # Define the output data directories.
@@ -107,7 +160,7 @@
     try:
         start = now = time()
 
-        i = importer.Importer(path, cache_dir, verbose)
+        i = importer.Importer(path, cache_dir, verbose, warnings)
         m = i.initialise(filename, reset)
         success = i.finalise()
 
diff -r aa11ebd14c79 -r c34d7d187b2c translator.py
--- a/translator.py	Wed Feb 08 16:20:27 2017 +0100
+++ b/translator.py	Wed Feb 08 17:24:31 2017 +0100
@@ -1215,9 +1215,11 @@
 
                 target_structure = "&%s" % encode_path(objpath)
 
-        # Other targets are retrieved at run-time.
-
-        else:
+        # Other targets are retrieved at run-time. Some information about them
+        # may be available and be used to provide warnings about argument
+        # compatibility.
+
+        elif self.importer.give_warning("args"):
             unsuitable = self.get_referenced_attribute_invocations(location)
 
             if unsuitable: