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c++: exhibit a safe symbol_type

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Instead of introducing make_symbol (whose name, btw, somewhat
infringes on the user's "name space", if she defines a token named
"symbol"), let's make the construction of symbol_type safer, using
assertions.

For instance with:

    %token ':' <std::string> ID <int> INT;

generate:

    symbol_type (int token, const std::string&);
    symbol_type (int token, const int&);
    symbol_type (int token);

It does mean that now named token constructors (make_ID, make_INT,
etc.) go through a useless assert, but I think we can ignore this: I
assume any decent compiler will inline the symbol_type ctor inside the
make_TOKEN functions, which will show that the assert is trivially
verified, hence I expect no code will be emitted for it.  And anyway,
that's an assert, NDEBUG controls it.

* data/c++.m4 (symbol_type): Turn into a subclass of
basic_symbol<by_type>.
Declare symbol constructors when variants are enabled.
* data/variant.hh (_b4_type_constructor_declare)
(_b4_type_constructor_define): Replace with...
(_b4_symbol_constructor_declare, _b4_symbol_constructor_def): these.
Generate symbol_type constructors.
* doc/bison.texi (Complete Symbols): Document.
* tests/types.at: Check.
This commit is contained in:
Akim Demaille
2018-12-19 17:51:10 +01:00
parent 1f4dd2671a
commit e5780041b9
5 changed files with 142 additions and 43 deletions
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24
tests/types.at
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@@ -288,6 +288,24 @@ m4_foreach([b4_skel], [[yacc.c], [glr.c], [lalr1.cc], [glr.cc]],
AT_VAL.build (std::pair<std::string, std::string> ("two", "deux"));],
[10:11, two:deux])
# Type-based token constructors on move-only types, and types with commas.
AT_TEST([%skeleton "]b4_skel["
%define api.value.type variant
%define api.token.constructor],
[[%token <std::pair<int, int>> '1' '2';]],
['1' '2'
{
std::cout << $1.first << ':' << $1.second << ", "
<< $2.first << ':' << $2.second << '\n';
}],
["12"],
[[typedef yy::parser::symbol_type symbol;
if (res)
return symbol (res, std::make_pair (res - '0', res - '0' + 1));
else
return symbol (res)]],
[1:2, 2:3])
# Move-only types, and variadic emplace.
AT_TEST([%skeleton "]b4_skel["
%code requires { #include <memory> }
@@ -336,11 +354,11 @@ m4_foreach([b4_skel], [[yacc.c], [glr.c], [lalr1.cc], [glr.cc]],
<< $2.first << ':' << $2.second << '\n'; }],
["12"],
[[if (res == '1')
return yy::parser::make_symbol ('1', std::make_unique<int> (10));
return {res, std::make_unique<int> (10)};
else if (res == '2')
return yy::parser::make_symbol ('2', std::make_pair (21, 22));
return {res, std::make_pair (21, 22)};
else
return yy::parser::make_symbol (0)]],
return res]],
[10, 21:22],
[AT_REQUIRE_CXX_STD(14, [echo "$at_std not supported"; continue])])