Improves main function

include/cpp2util.h

@@ -199,6 +199,9 @@
     #include <cstddef>
     #include <utility>
     #include <cstdio>
+    #include <vector>
+    #include <string_view>
+    #include <span>
 
     #if defined(CPP2_USE_SOURCE_LOCATION)
         #include <source_location>
@@ -297,7 +300,6 @@ constexpr auto contract_group::set_handler(handler h) -> handler {
     return old;
 }
 
-
 //  Null pointer deref checking
 //
 auto assert_not_null(auto&& p CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAULT) -> auto&&
@@ -326,7 +328,6 @@ auto assert_in_bounds(auto&& x, auto&& arg CPP2_SOURCE_LOCATION_PARAM_WITH_DEFAU
     return std::forward<decltype(x)>(x) [ std::forward<decltype(arg)>(arg) ];
 }
 
-
 //-----------------------------------------------------------------------
 //
 //  Arena objects for std::allocators
@@ -825,6 +826,41 @@ inline auto to_string(std::tuple<Ts...> const& t) -> std::string
     }
 }
 
+// Helper to convert the arguments of main to safer type.
+inline auto convert_main_args(int argc, char** argv) -> std::vector<std::string_view>
+{
+    std::vector<std::string_view> args;
+    for (int i = 0; i < argc; ++i) {
+        args.push_back(argv[i]);
+    }
+    args.shrink_to_fit();
+    return args;
+}
+
+#define CPP2_MAIN_VOID_NO_ARGS \
+    int main() { \
+        cpp2__main(); \
+        return 0; \
+    }
+
+#define CPP2_MAIN_INT_NO_ARGS \
+    int main() { \
+        return cpp2__main(); \
+    }
+
+#define CPP2_MAIN_VOID_ARGS \
+    int main(int argc, char** argv) { \
+        auto args = cpp2::convert_main_args(argc, argv); \
+        cpp2__main(std::span{args}); \
+        return 0; \
+    }
+
+#define CPP2_MAIN_INT_ARGS \
+    int main(int argc, char** argv) { \
+        auto args = cpp2::convert_main_args(argc, argv); \
+        return cpp2__main(std::span{args}); \
+    }
+
 
 //-----------------------------------------------------------------------
 //
@@ -881,7 +917,6 @@ inline auto fopen( const char* filename, const char* mode ) {
 
 }
 
-
 using cpp2::cpp2_new;
 
 

regression-tests/mixed-bounds-check.cpp2

@@ -1,7 +1,7 @@
 
 #include <vector>
 
-main: () -> int = {
+main: () = {
     v : std::vector = (1, 2, 3, 4, 5);
     std::cout << v[5] << "\n";
 }

regression-tests/mixed-bounds-safety-with-assert-2.cpp2

@@ -1,5 +1,5 @@
 
-main: () -> int = {
+main: () = {
     v: std::vector<int> = (1, 2, 3, 4, 5);
     add_42_to_subrange(v, 1, 3);
 

regression-tests/mixed-bounds-safety-with-assert.cpp2

@@ -1,5 +1,5 @@
 
-main: () -> int = {
+main: () = {
     v: std::vector<int> = (1, 2, 3, 4, 5);
     print_subrange(v, 1, 13);
 }

regression-tests/mixed-captures-in-expressions-and-postconditions.cpp2

@@ -2,7 +2,7 @@
 #include <algorithm>
 #include <vector>
 
-main: () -> int = {
+main: () = {
     vec: std::vector<std::string>
             = ("hello", "2022");
 

regression-tests/mixed-function-expression-and-std-for-each.cpp2

@@ -4,7 +4,7 @@
 #include <algorithm>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     vec: std::vector<std::string> 
             = ("hello", "2022");
     view: std::span = vec;

regression-tests/mixed-function-expression-and-std-ranges-for-each-with-capture.cpp2

@@ -5,7 +5,7 @@
 #include <algorithm>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     vec: std::vector<std::string> 
             = ("hello", "2022");
     view: std::span = vec;

regression-tests/mixed-function-expression-and-std-ranges-for-each.cpp2

@@ -5,7 +5,7 @@
 #include <algorithm>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     vec: std::vector<std::string> 
             = ("hello", "2022");
     view: std::span = vec;

regression-tests/mixed-function-expression-with-pointer-capture.cpp2

@@ -5,7 +5,7 @@
 #include <algorithm>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     vec: std::vector<std::string> 
             = ("hello", "2023");
     view: std::span = vec;

regression-tests/mixed-function-expression-with-repeated-capture.cpp2

@@ -5,7 +5,7 @@
 #include <algorithm>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     vec: std::vector<std::string> 
             = ("hello", "2022");
     view: std::span = vec;

regression-tests/mixed-initialization-safety-1.cpp2

@@ -16,7 +16,7 @@ fill: (
     x = value.substr(0, count);
 }
 
-main: () -> int =
+main: () =
 {
     x: std::string;         // note: uninitialized!
 

regression-tests/mixed-initialization-safety-2.cpp2

@@ -16,7 +16,7 @@ fill: (
     x = value.substr(0, count);
 }
 
-main: () -> int =
+main: () =
 {
     x: std::string;         // note: uninitialized!
 

regression-tests/mixed-initialization-safety-3.cpp2

@@ -2,7 +2,7 @@
 #include <vector>
 #include <ctime>
 
-main: () -> int = {
+main: () = {
     x: std::string;         // note: uninitialized!
 
     if flip_a_coin() {

regression-tests/mixed-intro-for-with-counter-include-last.cpp2

@@ -1,5 +1,5 @@
 
-main: () -> int
+main: ()
 = {
     v: std::vector<int> = (1, 2, 3, 4, 5);
     counter := 42;

regression-tests/mixed-lifetime-safety-and-null-contracts.cpp2

@@ -3,7 +3,7 @@
 #include <vector>
 #include <string>
 
-main: () -> int = {
+main: () = {
     cpp2::Null.set_handler(call_my_framework&);
     try_pointer_stuff();
     std::cout << "done\n";

regression-tests/mixed-lifetime-safety-pointer-init-1.cpp2

@@ -2,7 +2,7 @@
 #include <cstdlib>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     x: int = 42;
     p: *int;
 

regression-tests/mixed-lifetime-safety-pointer-init-2.cpp2

@@ -2,7 +2,7 @@
 #include <cstdlib>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     x: int = 42;
     p: *int;
 

regression-tests/mixed-lifetime-safety-pointer-init-3.cpp2

@@ -2,7 +2,7 @@
 #include <cstdlib>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     x: int = 42;
     p: *int;
 

regression-tests/mixed-lifetime-safety-pointer-init-4.cpp2

@@ -2,7 +2,7 @@
 #include <cstdlib>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     x: int = 42;
     y: int = 43;
     p: *int;

regression-tests/mixed-parameter-passing-with-forward.cpp2

@@ -39,4 +39,4 @@ parameter_styles: (
 
 }
 
-main: () -> int = { }
+main: () = { }

regression-tests/mixed-parameter-passing.cpp2

@@ -37,4 +37,4 @@ parameter_styles: (
 
 }
 
-main: () -> int = { }
+main: () = { }

regression-tests/mixed-postexpression-with-capture.cpp2

@@ -5,7 +5,7 @@
 #include <algorithm>
 #include <iostream>
 
-main: () -> int = {
+main: () = {
     insert_at( 0, 42 );
 }
 

regression-tests/mixed-postfix-expression-custom-formatting.cpp2

@@ -12,4 +12,4 @@ test: (a:_) -> std::string = {
         );
 }
 
-main: () -> int = { }
+main: () = { }

regression-tests/mixed-string-interpolation.cpp2

@@ -5,7 +5,7 @@
 
 struct custom_struct_with_no_stringize_customization { } custom;
 
-main: () -> int = {
+main: () = {
     a := 2;
     b: std::optional<int> = ();
     std::cout << "a = (a)$, b = (b)$\n";

regression-tests/mixed-type-safety-1.cpp2

@@ -23,7 +23,7 @@ print: ( msg: std::string, b: bool ) =
 
 //--- examples -------------------------
 
-main: () -> int = 
+main: () =
 {
     print( "1.1 is int? ", 1.1 is int );
     print( "1   is int? ", 1   is int );

regression-tests/pure2-bounds-safety-pointer-arithmetic-error.cpp2

@@ -1,5 +1,5 @@
 
-main: () -> int
+main: ()
 = {
     words: std::vector<std::string> = ( "decorated", "hello", "world" );
 

regression-tests/pure2-bounds-safety-span.cpp2

@@ -1,5 +1,5 @@
 
-main: () -> int
+main: ()
 = {
     words: std::vector<std::string> = ( "decorated", "hello", "world" );
 

regression-tests/pure2-bugfix-for-name-lookup-and-value-decoration.cpp2

@@ -3,7 +3,7 @@ vals: () -> (i : int) = {
     return;
 }
 
-main: () -> int = {
+main: () = {
     v := vals();
     v.i;
 }

regression-tests/pure2-hello.cpp2

@@ -1,5 +1,5 @@
 
-main: () -> int = {
+main: () = {
     std::cout << "Hello " << name() << "\n";
 }
 

regression-tests/pure2-inspect-expression-in-generic-function-multiple-types.cpp2

@@ -1,4 +1,4 @@
-main: () -> int = {
+main: () = {
     v: std::variant<int, double> = 42.0;
     a: std::any = "xyzzy" as std::string;
     o: std::optional<int> = ();

regression-tests/pure2-inspect-expression-with-as-in-generic-function.cpp2

@@ -1,4 +1,4 @@
-main: () -> int = {
+main: () = {
     print_an_int("syzygy");
     print_an_int(1);
     print_an_int(1.1);

regression-tests/pure2-inspect-fallback-with-variant-any-optional.cpp2

@@ -1,5 +1,5 @@
 
-main: () -> int = {
+main: () = {
     v: std::variant<int, std::string> = "xyzzy" as std::string;
     a: std::any = "xyzzy" as std::string;
     o: std::optional<std::string> = "xyzzy" as std::string;

regression-tests/pure2-inspect-generic-void-empty-with-variant-any-optional.cpp2

@@ -1,5 +1,5 @@
 
-main: () -> int = {
+main: () = {
     p: std::unique_ptr<int> = ();
     i: std::vector<int>::iterator = ();
     v: std::variant<std::monostate, int, std::string> = ();
@@ -23,4 +23,4 @@ test_generic: ( x: _ ) = {
             is _   = " no match";
         }
         << "\n";
-}
+}

regression-tests/pure2-int-main-arg.cpp2

@@ -0,0 +1,4 @@
+main: (move args :std::span<std::string_view>) -> int = {
+    for args do: (arg: _) = std::cout << arg << '\n';
+    return 0;
+}

regression-tests/pure2-intro-example-hello-2022.cpp2

@@ -1,4 +1,4 @@
-main: () -> int = {
+main: () = {
     vec: std::vector<std::string> 
             = ("hello", "2022");
     view: std::span = vec;

regression-tests/pure2-intro-example-three-loops.cpp2

@@ -7,7 +7,7 @@ decorate_and_print: (inout thing:_) = {
     print(thing);
 }
 
-main: () -> int = {
+main: () = {
     words: std::vector<std::string> =
         ( "hello", "big", "world" );
     view: std::span<std::string> = words;

regression-tests/pure2-lifetime-safety-pointer-init-1.cpp2

@@ -1,5 +1,5 @@
 
-main: () -> int = {
+main: () = {
     x: int = 42;
     p: *int;
 

regression-tests/pure2-lifetime-safety-reject-null.cpp2

@@ -3,7 +3,7 @@
 #include <vector>
 #include <string>
 
-main: () -> int
+main: ()
 = {
     words: std::vector<std::string> = ( "decorated", "hello", "world" );
 

regression-tests/pure2-stdio-with-raii.cpp2

@@ -1,7 +1,7 @@
 
 //  "A better C than C" ... ?
 //
-main: () -> int = {
+main: () = {
     s: std::string = "Freddy";
     myfile := cpp2::fopen("xyzzy", "w");
     myfile.fprintf( "Hello %s with UFCS!", s.c_str() );

regression-tests/pure2-stdio.cpp2

@@ -1,7 +1,7 @@
 
 //  "A better C than C" ... ?
 //
-main: () -> int = {
+main: () = {
     s: std::string = "Fred";
     myfile := fopen("xyzzy", "w");
     myfile.fprintf( "Hello %s with UFCS!", s.c_str() );