3273

Undo 3272. The trouble with creating a new section for constants is that
there's no good place to order it since constants can be initialized
using globals as well as vice versa. And I don't want to add constraints
disallowing either side.

Instead, a new plan: always declare constants in the Globals section
using 'extern const' rather than just 'const', since otherwise constants
implicitly have internal linkage (http://stackoverflow.com/questions/14894698/why-does-extern-const-int-n-not-work-as-expected)

000organization.cc

@@ -94,20 +94,22 @@
 // Types
 // End Types
 
-// prototypes are auto-generated in the makefile; define your functions in any order
+// Prototypes are auto-generated in the makefile; define your functions in any
+// order. Just be sure to declare each function header all on one line. Our
+// auto-generation scripts are too minimal and simple-minded to handle
+// anything else.
 #include "function_list"  // by convention, files ending with '_list' are auto-generated
 
 // Globals
 //
-// (Code in this section should strictly consist only of single-line variable
-// definitions; the makefile will simplistically auto-generate extern
-// declarations for them.)
+// All statements in this section should always define a single variable on a
+// single line. The makefile will simple-mindedly auto-generate extern
+// declarations for them. Don't forget to define (not just declare) constants
+// with extern linkage in this section, since C++ global constants have
+// internal linkage by default.
 //
 // End Globals
 
-// Constants
-// End Constants
-
 int main(int argc, char* argv[]) {
   atexit(teardown);
 

002test.cc

@@ -10,7 +10,8 @@
 
 :(before "End Types")
 typedef void (*test_fn)(void);
-:(before "End Constants")
+:(before "Globals")
+// move a global ahead into types that we can't generate an extern declaration for
 const test_fn Tests[] = {
   #include "test_list"  // auto-generated; see makefile
 };

003trace.cc

@@ -92,7 +92,9 @@ bool Hide_errors = false;
 Hide_errors = false;
 
 :(before "End Types")
-// pre-define some globals that trace_stream needs to know about
+// Pre-define some global constants that trace_stream needs to know about.
+// Since they're in the Types section, they'll be included in any cleaved
+// compilation units. So no extern linkage.
 const int Max_depth = 9999;
 const int Error_depth = 0;  // definitely always print errors
 const int App_depth = 2;  // temporarily where all mu code will trace to
@@ -383,14 +385,14 @@ using std::ofstream;
 
 #include "termbox/termbox.h"
 
-:(before "End Constants")
+:(before "End Globals")
 //: In future layers we'll use the depth field as follows:
 //:
 //: Errors will be depth 0.
 //: Mu 'applications' will be able to use depths 1-100 as they like.
 //: Primitive statements will occupy 101-9989
-const int Initial_callstack_depth = 101;
-const int Max_callstack_depth = 9989;
+extern const int Initial_callstack_depth = 101;
+extern const int Max_callstack_depth = 9989;
 //: Finally, details of primitive mu statements will occupy depth 9990-9999 (more on that later as well)
 //:
 //: This framework should help us hide some details at each level, mixing

010vm.cc

@@ -412,8 +412,8 @@ string_tree* property(const reagent& r, const string& name) {
   return NULL;
 }
 
-:(before "End Constants")
-const string Ignore(",");  // commas are ignored in mu except within [] strings
+:(before "End Globals")
+extern const string Ignore(",");  // commas are ignored in mu except within [] strings
 :(code)
 void skip_whitespace_but_not_newline(istream& in) {
   while (true) {

011load.cc

@@ -155,9 +155,9 @@ string next_word(istream& in) {
   return out.str();
 }
 
-:(before "End Constants")
+:(before "End Globals")
 // word boundaries
-const string Terminators("(){}");
+extern const string Terminators("(){}");
 :(code)
 void slurp_word(istream& in, ostream& out) {
   char c;

034address.cc

@@ -245,7 +245,7 @@ void transform_new_to_allocate(const recipe_ordinal r) {
 //: implement 'allocate' based on size
 
 :(before "End Globals")
-const int Reserved_for_tests = 1000;
+extern const int Reserved_for_tests = 1000;
 int Memory_allocated_until = Reserved_for_tests;
 int Initial_memory_per_routine = 100000;
 :(before "End Setup")

050scenario.cc

@@ -159,6 +159,7 @@ for (int i = 0; i < SIZE(Scenarios); ++i) {
 }
 
 :(before "End Globals")
+// this isn't a constant, just a global of type const*
 const scenario* Current_scenario = NULL;
 :(code)
 void run_mu_scenario(const scenario& s) {

055shape_shifting_container.cc

@@ -79,13 +79,13 @@ container foo:t [
 ]
 +error: foo: type ingredient 't' must begin with an underscore
 
-:(before "End Constants")
+:(before "End Globals")
 // We'll use large type ordinals to mean "the following type of the variable".
 // For example, if we have a generic type called foo:_elem, the type
 // ingredient _elem in foo's type_info will have value START_TYPE_INGREDIENTS,
 // and we'll handle it by looking in the current reagent for the next type
 // that appears after foo.
-const int START_TYPE_INGREDIENTS = 2000;
+extern const int START_TYPE_INGREDIENTS = 2000;
 :(before "End Commandline Parsing")  // after loading .mu files
 assert(Next_type_ordinal < START_TYPE_INGREDIENTS);
 

082scenario_screen.cc

@@ -133,7 +133,7 @@ $error: 0
 //: locations.
 
 :(before "End Globals")
-const int Max_variables_in_scenarios = Reserved_for_tests-100;
+extern const int Max_variables_in_scenarios = Reserved_for_tests-100;
 int Next_predefined_global_for_scenarios = Max_variables_in_scenarios;
 :(before "End Setup")
 assert(Next_predefined_global_for_scenarios < Reserved_for_tests);
@@ -143,10 +143,10 @@ assert(Next_predefined_global_for_scenarios < Reserved_for_tests);
 // initialize a default-space.
 assert(Name[tmp_recipe.at(0)][""] < Max_variables_in_scenarios);
 
-:(before "End Constants")
-// Fixed Scenario Locations.
-const int SCREEN = Next_predefined_global_for_scenarios++;
-// End Fixed Scenario Locations.
+:(before "End Globals")
+// Scenario Globals.
+extern const int SCREEN = Next_predefined_global_for_scenarios++;
+// End Scenario Globals.
 
 //: give 'screen' a fixed location in scenarios
 :(before "End Special Scenario Variable Names(r)")

085scenario_console.cc

@@ -33,8 +33,8 @@ scenario keyboard-in-scenario [
   ]
 ]
 
-:(before "End Fixed Scenario Locations")
-const int CONSOLE = Next_predefined_global_for_scenarios++;
+:(before "End Scenario Globals")
+extern const int CONSOLE = Next_predefined_global_for_scenarios++;
 //: give 'console' a fixed location in scenarios
 :(before "End Special Scenario Variable Names(r)")
 Name[r]["console"] = CONSOLE;

089scenario_filesystem.cc

@@ -72,8 +72,8 @@ scenario assume-filesystem [
   ]
 ]
 
-:(before "End Fixed Scenario Locations")
-const int FILESYSTEM = Next_predefined_global_for_scenarios++;
+:(before "End Globals")
+extern const int FILESYSTEM = Next_predefined_global_for_scenarios++;
 //: give 'filesystem' a fixed location in scenarios
 :(before "End Special Scenario Variable Names(r)")
 Name[r]["filesystem"] = FILESYSTEM;