This is my attempt to implement P0305R1, Selection statements with initializer.
It allows the users to write
if (init; cond) // ...
which is equivalent to
{
init
if (cond) // ...
}
Similarly for if-else, if constexpr, and switch.
The approach I had taken was to tentatively parse "init" and if no semicolon
follows, abort the parse and just parse the condition. But this didn't work.
An init-statement is either a simple-declaration or an expression-statement,
and parsing either has irreversible side-effects--e.g. adding a new statement
or a new declaration, or duplicating side-effects. Using firewalls here
doesn't help. Since an init-statement ends with a semicolon, I decided to
write cp_parser_init_statement_p, which checks if there's a semicolon in the if
condition that is not nested in () or in {} (think of ({}) or lambda
expressions). It seemed a bit weird but seems to work well. And then it's
just a simple matter of calling cp_parser_init_statement that parses either a
simple declaration or an expression statement and does the right thing wrt
scopes.
Since "for-init-statement" is no longer in the standard, I renamed all the
occurrences to "init-statement".
There's also this -ffor-scope thing, but I didn't touch it and it's probably
not necessary to.
Bootstrapped/regtested on x86_64-linux and ppc64-linux, ok for trunk?
2016-10-05 Marek Polacek <pola...@redhat.com>
Implement P0305R1, Selection statements with initializer.
* cp-array-notation.c (create_an_loop): Call finish_init_stmt
instead of finish_for_init_stmt.
* cp-tree.h (finish_for_init_stmt): Rename to finish_init_stmt.
* decl.c (poplevel): Adjust a comment.
* init.c (build_vec_init): Call finish_init_stmt instead of
finish_for_init_stmt.
* name-lookup.c (pushdecl_maybe_friend_1): Adjust a comment.
* name-lookup.h (enum scope_kind): Likewise.
* parser.c (cp_parser_statement): Update commentary.
(cp_parser_init_statement_p): New function.
(cp_parser_selection_statement): Parse the optional init-statement.
(cp_parser_for): Call finish_init_stmt instead of finish_for_init_stmt.
(cp_parser_c_for): Likewise.
(cp_convert_range_for): Call finish_init_stmt instead of
finish_for_init_stmt.
(cp_parser_range_for_member_function): Update commentary.
(cp_parser_iteration_statement):
(cp_parser_for_init_statement): Rename to cp_parser_init_statement.
* pt.c (tsubst_omp_for_iterator): Update commentary.
(tsubst_expr): Call finish_init_stmt instead of finish_for_init_stmt.
* semantics.c (finish_for_init_stmt): Rename to finish_init_stmt.
Update commentary.
* g++.dg/cpp1z/init-statement1.C: New test.
* g++.dg/cpp1z/init-statement2.C: New test.
* g++.dg/cpp1z/init-statement3.C: New test.
* g++.dg/cpp1z/init-statement4.C: New test.
* g++.dg/cpp1z/init-statement5.C: New test.
* g++.dg/cpp1z/init-statement6.C: New test.
* g++.dg/cpp1z/init-statement7.C: New test.
diff --git gcc/cp/cp-array-notation.c gcc/cp/cp-array-notation.c
index 4687ced..633ab09 100644
--- gcc/cp/cp-array-notation.c
+++ gcc/cp/cp-array-notation.c
@@ -66,7 +66,7 @@ create_an_loop (tree init, tree cond, tree incr, tree body)
finish_expr_stmt (init);
for_stmt = begin_for_stmt (NULL_TREE, NULL_TREE);
- finish_for_init_stmt (for_stmt);
+ finish_init_stmt (for_stmt);
finish_for_cond (cond, for_stmt, false);
finish_for_expr (incr, for_stmt);
finish_expr_stmt (body);
diff --git gcc/cp/cp-tree.h gcc/cp/cp-tree.h
index 3fbe1d9..92e4017 100644
--- gcc/cp/cp-tree.h
+++ gcc/cp/cp-tree.h
@@ -6297,7 +6297,7 @@ extern void finish_do_stmt (tree,
tree, bool);
extern tree finish_return_stmt (tree);
extern tree begin_for_scope (tree *);
extern tree begin_for_stmt (tree, tree);
-extern void finish_for_init_stmt (tree);
+extern void finish_init_stmt (tree);
extern void finish_for_cond (tree, tree, bool);
extern void finish_for_expr (tree, tree);
extern void finish_for_stmt (tree);
diff --git gcc/cp/decl.c gcc/cp/decl.c
index 6646062..6a08d8f 100644
--- gcc/cp/decl.c
+++ gcc/cp/decl.c
@@ -639,9 +639,8 @@ poplevel (int keep, int reverse, int functionbody)
BLOCK_SUPERCONTEXT (link) = block;
/* We still support the old for-scope rules, whereby the variables
- in a for-init statement were in scope after the for-statement
- ended. We only use the new rules if flag_new_for_scope is
- nonzero. */
+ in a init statement were in scope after the for-statement ended.
+ We only use the new rules if flag_new_for_scope is nonzero. */
leaving_for_scope
= current_binding_level->kind == sk_for && flag_new_for_scope == 1;
diff --git gcc/cp/init.c gcc/cp/init.c
index 2d5877d..d1c8274 100644
--- gcc/cp/init.c
+++ gcc/cp/init.c
@@ -4052,7 +4052,7 @@ build_vec_init (tree base, tree maxindex, tree init,
tree to;
for_stmt = begin_for_stmt (NULL_TREE, NULL_TREE);
- finish_for_init_stmt (for_stmt);
+ finish_init_stmt (for_stmt);
finish_for_cond (build2 (GT_EXPR, boolean_type_node, iterator,
build_int_cst (TREE_TYPE (iterator), -1)),
for_stmt, false);
diff --git gcc/cp/name-lookup.c gcc/cp/name-lookup.c
index 1bce63b..9e84a1b 100644
--- gcc/cp/name-lookup.c
+++ gcc/cp/name-lookup.c
@@ -1156,7 +1156,7 @@ pushdecl_maybe_friend_1 (tree x, bool is_friend)
}
}
/* Error if redeclaring a local declared in a
- for-init-statement or in the condition of an if or
+ init-statement or in the condition of an if or
switch statement when the new declaration is in the
outermost block of the controlled statement.
Redeclaring a variable from a for or while condition is
diff --git gcc/cp/name-lookup.h gcc/cp/name-lookup.h
index 2cb129c..fd71038 100644
--- gcc/cp/name-lookup.h
+++ gcc/cp/name-lookup.h
@@ -107,7 +107,7 @@ enum scope_kind {
sk_try, /* A try-block. */
sk_catch, /* A catch-block. */
sk_for, /* The scope of the variable declared in a
- for-init-statement. */
+ init-statement. */
sk_cond, /* The scope of the variable declared in the condition
of an if or switch statement. */
sk_function_parms, /* The scope containing function parameters. */
diff --git gcc/cp/parser.c gcc/cp/parser.c
index 683a6dd..03c007e 100644
--- gcc/cp/parser.c
+++ gcc/cp/parser.c
@@ -2117,7 +2117,7 @@ static tree cp_parser_condition
(cp_parser *);
static tree cp_parser_iteration_statement
(cp_parser *, bool *, bool);
-static bool cp_parser_for_init_statement
+static bool cp_parser_init_statement
(cp_parser *, tree *decl);
static tree cp_parser_for
(cp_parser *, bool);
@@ -2642,6 +2642,8 @@ static bool cp_parser_compound_literal_p
(cp_parser *);
static bool cp_parser_array_designator_p
(cp_parser *);
+static bool cp_parser_init_statement_p
+ (cp_parser *);
static bool cp_parser_skip_to_closing_square_bracket
(cp_parser *);
@@ -10396,6 +10398,10 @@ cp_parser_lambda_body (cp_parser* parser, tree
lambda_expr)
declaration-statement
attribute-specifier-seq (opt) try-block
+ init-statement:
+ expression-statement
+ simple-declaration
+
TM Extension:
statement:
@@ -10936,12 +10942,65 @@ cp_parser_statement_seq_opt (cp_parser* parser, tree
in_statement_expr)
}
}
+/* Return true if we're looking at (init; cond), false otherwise. */
+
+static bool
+cp_parser_init_statement_p (cp_parser *parser)
+{
+ unsigned paren_depth = 0;
+ unsigned brace_depth = 0;
+
+ /* Look for ';' that is not nested in () or {}. */
+ while (true)
+ {
+ cp_token *token = cp_lexer_peek_token (parser->lexer);
+
+ switch (token->type)
+ {
+ case CPP_EOF:
+ case CPP_PRAGMA_EOL:
+ /* If we've run out of tokens, stop. */
+ return false;
+
+ case CPP_SEMICOLON:
+ if (paren_depth == 0 && brace_depth == 0)
+ return true;
+ break;
+
+ case CPP_CLOSE_PAREN:
+ /* If the next token is a non-nested '(', then we have reached
+ the end of the if condition. */
+ if (paren_depth-- == 0)
+ return false;
+ break;
+
+ case CPP_OPEN_PAREN:
+ ++paren_depth;
+ break;
+
+ case CPP_CLOSE_BRACE:
+ --brace_depth;
+ break;
+
+ case CPP_OPEN_BRACE:
+ ++brace_depth;
+ break;
+
+ default:
+ break;
+ }
+
+ /* Consume the token. */
+ cp_lexer_consume_token (parser->lexer);
+ }
+}
+
/* Parse a selection-statement.
selection-statement:
- if ( condition ) statement
- if ( condition ) statement else statement
- switch ( condition ) statement
+ if ( init-statement [opt] condition ) statement
+ if ( init-statement [opt] condition ) statement else statement
+ switch ( init-statement [opt] condition ) statement
Returns the new IF_STMT or SWITCH_STMT.
@@ -11006,6 +11065,21 @@ cp_parser_selection_statement (cp_parser* parser, bool
*if_p,
else
statement = begin_switch_stmt ();
+ /* Parse the optional init-statement. */
+ tree decl;
+ cp_lexer_save_tokens (parser->lexer);
+ const bool init_stmt_p = cp_parser_init_statement_p (parser);
+ /* Roll back the tokens we skipped. */
+ cp_lexer_rollback_tokens (parser->lexer);
+ if (init_stmt_p)
+ {
+ if (cxx_dialect < cxx1z)
+ pedwarn (cp_lexer_peek_token (parser->lexer)->location, 0,
+ "init-statement in selection statements only available "
+ "with -std=c++1z or -std=gnu++1z");
+ cp_parser_init_statement (parser, &decl);
+ }
+
/* Parse the condition. */
condition = cp_parser_condition (parser);
/* Look for the `)'. */
@@ -11306,7 +11380,7 @@ cp_parser_for (cp_parser *parser, bool ivdep)
scope = begin_for_scope (&init);
/* Parse the initialization. */
- is_range_for = cp_parser_for_init_statement (parser, &decl);
+ is_range_for = cp_parser_init_statement (parser, &decl);
if (is_range_for)
return cp_parser_range_for (parser, scope, init, decl, ivdep);
@@ -11323,9 +11397,9 @@ cp_parser_c_for (cp_parser *parser, tree scope, tree
init, bool ivdep)
tree stmt;
stmt = begin_for_stmt (scope, init);
- /* The for-init-statement has already been parsed in
- cp_parser_for_init_statement, so no work is needed here. */
- finish_for_init_stmt (stmt);
+ /* The init-statement has already been parsed in
+ cp_parser_init_statement, so no work is needed here. */
+ finish_init_stmt (stmt);
/* If there's a condition, process it. */
if (cp_lexer_next_token_is_not (parser->lexer, CPP_SEMICOLON))
@@ -11354,7 +11428,7 @@ cp_parser_c_for (cp_parser *parser, tree scope, tree
init, bool ivdep)
decl-specifier-seq declarator : expression
The decl-specifier-seq declarator and the `:' are already parsed by
- cp_parser_for_init_statement. If processing_template_decl it returns a
+ cp_parser_init_statement. If processing_template_decl it returns a
newly created RANGE_FOR_STMT; if not, it is converted to a
regular FOR_STMT. */
@@ -11552,7 +11626,7 @@ cp_convert_range_for (tree statement, tree range_decl,
tree range_expr,
/*is_constant_init*/false, NULL_TREE,
LOOKUP_ONLYCONVERTING);
- finish_for_init_stmt (statement);
+ finish_init_stmt (statement);
/* The new for condition. */
condition = build_x_binary_op (input_location, NE_EXPR,
@@ -11726,7 +11800,7 @@ cp_parser_range_for_member_function (tree range, tree
identifier)
iteration-statement:
while ( condition ) statement
do statement while ( expression ) ;
- for ( for-init-statement condition [opt] ; expression [opt] )
+ for ( init-statement condition [opt] ; expression [opt] )
statement
Returns the new WHILE_STMT, DO_STMT, FOR_STMT or RANGE_FOR_STMT. */
@@ -11832,15 +11906,15 @@ cp_parser_iteration_statement (cp_parser* parser,
bool *if_p, bool ivdep)
return statement;
}
-/* Parse a for-init-statement or the declarator of a range-based-for.
+/* Parse a init-statement or the declarator of a range-based-for.
Returns true if a range-based-for declaration is seen.
- for-init-statement:
+ init-statement:
expression-statement
simple-declaration */
static bool
-cp_parser_for_init_statement (cp_parser* parser, tree *decl)
+cp_parser_init_statement (cp_parser* parser, tree *decl)
{
/* If the next token is a `;', then we have an empty
expression-statement. Grammatically, this is also a
diff --git gcc/cp/pt.c gcc/cp/pt.c
index e6b1368..e6bacdf 100644
--- gcc/cp/pt.c
+++ gcc/cp/pt.c
@@ -14974,7 +14974,7 @@ tsubst_omp_for_iterator (tree t, int i, tree declv,
tree orig_declv,
if (init && TREE_CODE (init) == DECL_EXPR)
{
/* We need to jump through some hoops to handle declarations in the
- for-init-statement, since we might need to handle auto deduction,
+ init-statement, since we might need to handle auto deduction,
but we need to keep control of initialization. */
decl_expr = init;
init = DECL_INITIAL (DECL_EXPR_DECL (init));
@@ -15359,7 +15359,7 @@ tsubst_expr (tree t, tree args, tsubst_flags_t
complain, tree in_decl,
case FOR_STMT:
stmt = begin_for_stmt (NULL_TREE, NULL_TREE);
RECUR (FOR_INIT_STMT (t));
- finish_for_init_stmt (stmt);
+ finish_init_stmt (stmt);
tmp = RECUR (FOR_COND (t));
finish_for_cond (tmp, stmt, false);
tmp = RECUR (FOR_EXPR (t));
diff --git gcc/cp/semantics.c gcc/cp/semantics.c
index 1d8f336..cae5afc 100644
--- gcc/cp/semantics.c
+++ gcc/cp/semantics.c
@@ -953,11 +953,11 @@ begin_for_stmt (tree scope, tree init)
return r;
}
-/* Finish the for-init-statement of a for-statement, which may be
+/* Finish the init-statement of a for-statement, which may be
given by FOR_STMT. */
void
-finish_for_init_stmt (tree for_stmt)
+finish_init_stmt (tree for_stmt)
{
if (processing_template_decl)
FOR_INIT_STMT (for_stmt) = pop_stmt_list (FOR_INIT_STMT (for_stmt));
diff --git gcc/testsuite/g++.dg/cpp1z/init-statement1.C
gcc/testsuite/g++.dg/cpp1z/init-statement1.C
index e69de29..fbe0d8b 100644
--- gcc/testsuite/g++.dg/cpp1z/init-statement1.C
+++ gcc/testsuite/g++.dg/cpp1z/init-statement1.C
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+extern int foo (void);
+extern void bar (int);
+
+void
+f (void)
+{
+ if (auto p = foo (); p > 10) // { dg-warning "init-statement" "" { target
c++14_down } }
+ bar (p);
+ else
+ bar (-p);
+}
diff --git gcc/testsuite/g++.dg/cpp1z/init-statement2.C
gcc/testsuite/g++.dg/cpp1z/init-statement2.C
index e69de29..8cfe1ab 100644
--- gcc/testsuite/g++.dg/cpp1z/init-statement2.C
+++ gcc/testsuite/g++.dg/cpp1z/init-statement2.C
@@ -0,0 +1,62 @@
+// { dg-options -std=c++1z }
+// Test C++17 selection statements with initializer, basic use.
+
+extern int foo (void);
+extern void bar (int);
+extern int g;
+
+void
+f (void)
+{
+ if (auto p = foo (); p > 10)
+ bar (p);
+ else
+ bar (-p);
+
+ if ((g += 2); g > 6)
+ bar (1);
+
+ if (auto a = 9, b = foo (); a + b > 10)
+ bar (a + b);
+ else
+ bar (a - b);
+
+ if (({ int a; 1;}))
+ bar (0);
+
+ if (auto i = foo (); i > 6)
+ bar (0);
+ else if (i++; i > 8)
+ bar (1);
+}
+
+extern void lock (void);
+
+void
+f2 (int i)
+{
+ if (lock (); i > 10)
+ ++i;
+ else
+ --i;
+}
+
+void
+f3 (int i)
+{
+ switch (i *= 2; auto idx = i)
+ {
+ case 4:
+ bar (3);
+ break;
+ default:
+ break;
+ }
+}
+
+void
+f4 (void)
+{
+ if constexpr (constexpr auto s = sizeof (int); s > 10)
+ foo ();
+}
diff --git gcc/testsuite/g++.dg/cpp1z/init-statement3.C
gcc/testsuite/g++.dg/cpp1z/init-statement3.C
index e69de29..c178eaf 100644
--- gcc/testsuite/g++.dg/cpp1z/init-statement3.C
+++ gcc/testsuite/g++.dg/cpp1z/init-statement3.C
@@ -0,0 +1,16 @@
+// { dg-do run }
+// { dg-options -std=c++1z }
+// Test C++17 selection statements with initializer, side-effects.
+
+int
+main ()
+{
+ int g = 0;
+
+ if (g++; g > 1)
+ __builtin_abort ();
+ if (++g; g > 2)
+ __builtin_abort ();
+ if (g != 2)
+ __builtin_abort ();
+}
diff --git gcc/testsuite/g++.dg/cpp1z/init-statement4.C
gcc/testsuite/g++.dg/cpp1z/init-statement4.C
index e69de29..a5f7d8b 100644
--- gcc/testsuite/g++.dg/cpp1z/init-statement4.C
+++ gcc/testsuite/g++.dg/cpp1z/init-statement4.C
@@ -0,0 +1,59 @@
+// { dg-options -std=c++1z }
+
+extern int foo (void);
+extern void bar (int), die (void);
+
+void
+f (void)
+{
+ if (auto i = foo (); i != -1)
+ bar (1);
+ else
+ die ();
+
+ i = 10; // { dg-error "not declared" }
+}
+
+void
+f2 (void)
+{
+ switch (auto i = foo (); i)
+ {
+ case 0:
+ bar (i + 1);
+ break;
+ case 1:
+ bar (i + 10);
+ break;
+ default:
+ break;
+ }
+
+ i = 10; // { dg-error "not declared" }
+}
+
+void
+f3 (void)
+{
+ if constexpr (constexpr auto i = sizeof (long); i < 2)
+ die ();
+ i = 4; // { dg-error "not declared" }
+}
+
+
+void
+f4 (void)
+{
+ {
+ if (auto i = foo (); i > -1)
+ {
+ if (i > 5)
+ bar (i);
+ if (auto j = foo (); true)
+ j++;
+ j--; // { dg-error "not declared" }
+ }
+ i = 10; // { dg-error "not declared" }
+ }
+ i = 10; // { dg-error "not declared" }
+}
diff --git gcc/testsuite/g++.dg/cpp1z/init-statement5.C
gcc/testsuite/g++.dg/cpp1z/init-statement5.C
index e69de29..6efa0ed 100644
--- gcc/testsuite/g++.dg/cpp1z/init-statement5.C
+++ gcc/testsuite/g++.dg/cpp1z/init-statement5.C
@@ -0,0 +1,16 @@
+// Testcase from P0305R1
+// { dg-options -std=c++1z }
+
+enum class status_code { SUCCESS };
+extern int get_value ();
+status_code bar (int);
+status_code do_more_stuff (void);
+
+status_code
+foo ()
+{
+ int n = get_value ();
+ if (status_code c = bar (n); c != status_code::SUCCESS) { return c; }
+ if (status_code c = do_more_stuff (); c != status_code::SUCCESS) { return c;
}
+ return status_code::SUCCESS;
+}
diff --git gcc/testsuite/g++.dg/cpp1z/init-statement6.C
gcc/testsuite/g++.dg/cpp1z/init-statement6.C
index e69de29..53b0d31 100644
--- gcc/testsuite/g++.dg/cpp1z/init-statement6.C
+++ gcc/testsuite/g++.dg/cpp1z/init-statement6.C
@@ -0,0 +1,25 @@
+// Testcase from P0305R1
+// { dg-options -std=c++1z }
+
+#include <string>
+#include <map>
+#include <algorithm>
+
+std::map<int, std::string> m;
+extern int xread (int *);
+extern void publish (int), raise (int);
+
+void
+foo ()
+{
+ if (auto it = m.find (10); it != m.end ()) { std::string s = it->second; }
+ if (char buf[10]; std::fgets(buf, 10, stdin)) { m[0] += buf; }
+ if (int s; int count = xread (&s)) { publish(count); raise(s); }
+
+ const char *s;
+ if (auto keywords = {"if", "for", "while"};
+ std::any_of(keywords.begin(), keywords.end(), [&s](const char* kw) {
return s == kw; }))
+ {
+ // whatever
+ }
+}
diff --git gcc/testsuite/g++.dg/cpp1z/init-statement7.C
gcc/testsuite/g++.dg/cpp1z/init-statement7.C
index e69de29..a67617e 100644
--- gcc/testsuite/g++.dg/cpp1z/init-statement7.C
+++ gcc/testsuite/g++.dg/cpp1z/init-statement7.C
@@ -0,0 +1,9 @@
+// { dg-do run }
+// { dg-options -std=c++1z }
+
+int
+main ()
+{
+ if (int i = 10, &ir = i; [=]{ return ir; }() != 10)
+ __builtin_abort ();
+}
Marek
