Re: [PATCH 3/3] c++: P1997 array-copy extensions: Assignment, return, etc. [PR103238]
On 11/21/21 21:51, Will Wray via Gcc-patches wrote:
This second patch completes the work of the first 'array-copy' patch to
provide first-cut implementations of all P1997 features. It adds:
* Assignments to arrays from array values,a = b;
* Placeholder auto in array declarations, auto cp[] = a;
* Array as a return type from functions WIP, auto f() -> T[N];
* Parsing of array pseudo-destructors a.~A()
(only parsing for now, untested)
Let's not accept the pseudo-destructor and silently ignore it. Either
we should delay the parsing change until the semantics are implemented,
or parse it and give a sorry().
Assignments a = b were easily allowed by changing branch conditions.
Assignments a = {e...} were trickier (a case not mentioned in P1997):
int a[16]; a = {0,1,1,2}; a = {}; // assignments from init-lists
The semantics is the same as for struct aggregates:
(1) Aggregate initialization of an rhs array of the lhs type
(so trailing elements with no initializer are value initialized)
(2) Copy-initialization of the lhs from the rhs.
The special case of an optionally-braced array value is allowed so that
a = b and a = {b} are generally equivalent for same type arrays a and b.
However, the now special-special case of assignment from a braced string-
literal currently only supports exact-match (same as for other arrays):
char a[4]; a={"c++"} /* OK */; a={"c"} /* FAILs but should work */;
Array return from function is work in progress. The tests show what works.
I'm stuck in unfamiliar territory so it's best to submit what I have to be
reviewed for hints on how to progress.
Let's split out array return into a separate patch for now. It also has
ABI implications.
Please try the patch; play, stress it, and report the FAILS.
PR c++/103238
gcc/c/ChangeLog:
* c-decl.c (grokdeclarator): Don't complain of array returns.
gcc/cp/ChangeLog:
* call.c (can_convert_array): Extend to include array inits.
(standard_conversion): No decay for same-type array. Call build_conv.
(implicit_conversion_1): Call reshape_init for arrays too.
* decl.c (grokdeclarator): Don't complain of array returns.
* parser.c (cp_parser_postfix_dot_deref_expression): parse array ~A().
* pt.c (tsubst_function_type): Array type return is not a failure.
(do_auto_deduction): Placeholder auto deduction of array element type.
* tree.c (lvalue_kind): clk_class should include array (I think?).
* typeck.c (cp_build_modify_expr): Call reshape init to strip optional
braces. Allow NOP_EXPR for array assignment.
(convert_for_assignment): New if-block for same-type array convert,
strips optional braces, but rejects STRING_CST rhs shorter than lhs.
gcc/testsuite/ChangeLog:
* g++.dg/init/array-copy10.C: New test. auto[] deduce 'after' PASSes
* g++.dg/init/array-copy11.C: New test. Array return 'before' XFAILs
* g++.dg/init/array-copy12.C: New test. Array return 'after' PASSes
* g++.dg/init/array-copy7.C: New test. Array assign 'before' XFAILs
* g++.dg/init/array-copy8.C: New test. Array assign 'after' PASSes
* g++.dg/init/array-copy9.C: New test. auto[] deduce 'before' XFAILs
---
gcc/c/c-decl.c | 2 +-
gcc/cp/call.c| 43 +++--
gcc/cp/decl.c| 2 +-
gcc/cp/parser.c | 4 +-
gcc/cp/pt.c | 13 +-
gcc/cp/tree.c| 3 +-
gcc/cp/typeck.c | 26 +--
gcc/testsuite/g++.dg/init/array-copy10.C | 57 +++
gcc/testsuite/g++.dg/init/array-copy11.C | 13 ++
gcc/testsuite/g++.dg/init/array-copy12.C | 79
gcc/testsuite/g++.dg/init/array-copy7.C | 40
gcc/testsuite/g++.dg/init/array-copy8.C | 56 ++
gcc/testsuite/g++.dg/init/array-copy9.C | 57 +++
13 files changed, 372 insertions(+), 23 deletions(-)
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 3e28a038095..031c43d189f 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -7055,7 +7055,7 @@ grokdeclarator (const struct c_declarator *declarator,
"returning a function");
type = integer_type_node;
}
- if (TREE_CODE (type) == ARRAY_TYPE)
+ if (TREE_CODE (type) == ARRAY_TYPE && !flag_array_copy)
{
if (name)
error_at (loc, "%qE declared as function returning an array",
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 4ee21c7bdbd..c73fb73d86e 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -908,29 +908,34 @@ static bool
can_convert_array (tree atype, tree from, int flags, tsubst_flags_t complain)
{
tree elttype = TREE_TYPE (atype);
- unsigne
Re: [PATCH 3/3] c++: P1997 array-copy extensions: Assignment, return, etc. [PR103238]
On Mon, Nov 22, 2021 at 3:42 PM Joseph Myers wrote: > > On Sun, 21 Nov 2021, Will Wray via Gcc-patches wrote: > > > gcc/c/ChangeLog: > > > > * c-decl.c (grokdeclarator): Don't complain of array returns. > > A C front-end change like this doesn't belong in a C++ patch Of course, thanks. I'll remove it. Hopefully it'll be back before long, in a compatible C array-copy patchset.
Re: [PATCH 3/3] c++: P1997 array-copy extensions: Assignment, return, etc. [PR103238]
On Sun, 21 Nov 2021, Will Wray via Gcc-patches wrote: > gcc/c/ChangeLog: > > * c-decl.c (grokdeclarator): Don't complain of array returns. A C front-end change like this doesn't belong in a C++ patch (I don't see any reason why this C++ patch would need such a C front-end change, it's not e.g. changing the interface to a function called from shared code but defined separately for both front ends). -- Joseph S. Myers jos...@codesourcery.com
[PATCH 3/3] c++: P1997 array-copy extensions: Assignment, return, etc. [PR103238]
This second patch completes the work of the first 'array-copy' patch to
provide first-cut implementations of all P1997 features. It adds:
* Assignments to arrays from array values,a = b;
* Placeholder auto in array declarations, auto cp[] = a;
* Array as a return type from functions WIP, auto f() -> T[N];
* Parsing of array pseudo-destructors a.~A()
(only parsing for now, untested)
Assignments a = b were easily allowed by changing branch conditions.
Assignments a = {e...} were trickier (a case not mentioned in P1997):
int a[16]; a = {0,1,1,2}; a = {}; // assignments from init-lists
The semantics is the same as for struct aggregates:
(1) Aggregate initialization of an rhs array of the lhs type
(so trailing elements with no initializer are value initialized)
(2) Copy-initialization of the lhs from the rhs.
The special case of an optionally-braced array value is allowed so that
a = b and a = {b} are generally equivalent for same type arrays a and b.
However, the now special-special case of assignment from a braced string-
literal currently only supports exact-match (same as for other arrays):
char a[4]; a={"c++"} /* OK */; a={"c"} /* FAILs but should work */;
Array return from function is work in progress. The tests show what works.
I'm stuck in unfamiliar territory so it's best to submit what I have to be
reviewed for hints on how to progress.
Please try the patch; play, stress it, and report the FAILS.
PR c++/103238
gcc/c/ChangeLog:
* c-decl.c (grokdeclarator): Don't complain of array returns.
gcc/cp/ChangeLog:
* call.c (can_convert_array): Extend to include array inits.
(standard_conversion): No decay for same-type array. Call build_conv.
(implicit_conversion_1): Call reshape_init for arrays too.
* decl.c (grokdeclarator): Don't complain of array returns.
* parser.c (cp_parser_postfix_dot_deref_expression): parse array ~A().
* pt.c (tsubst_function_type): Array type return is not a failure.
(do_auto_deduction): Placeholder auto deduction of array element type.
* tree.c (lvalue_kind): clk_class should include array (I think?).
* typeck.c (cp_build_modify_expr): Call reshape init to strip optional
braces. Allow NOP_EXPR for array assignment.
(convert_for_assignment): New if-block for same-type array convert,
strips optional braces, but rejects STRING_CST rhs shorter than lhs.
gcc/testsuite/ChangeLog:
* g++.dg/init/array-copy10.C: New test. auto[] deduce 'after' PASSes
* g++.dg/init/array-copy11.C: New test. Array return 'before' XFAILs
* g++.dg/init/array-copy12.C: New test. Array return 'after' PASSes
* g++.dg/init/array-copy7.C: New test. Array assign 'before' XFAILs
* g++.dg/init/array-copy8.C: New test. Array assign 'after' PASSes
* g++.dg/init/array-copy9.C: New test. auto[] deduce 'before' XFAILs
---
gcc/c/c-decl.c | 2 +-
gcc/cp/call.c| 43 +++--
gcc/cp/decl.c| 2 +-
gcc/cp/parser.c | 4 +-
gcc/cp/pt.c | 13 +-
gcc/cp/tree.c| 3 +-
gcc/cp/typeck.c | 26 +--
gcc/testsuite/g++.dg/init/array-copy10.C | 57 +++
gcc/testsuite/g++.dg/init/array-copy11.C | 13 ++
gcc/testsuite/g++.dg/init/array-copy12.C | 79
gcc/testsuite/g++.dg/init/array-copy7.C | 40
gcc/testsuite/g++.dg/init/array-copy8.C | 56 ++
gcc/testsuite/g++.dg/init/array-copy9.C | 57 +++
13 files changed, 372 insertions(+), 23 deletions(-)
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 3e28a038095..031c43d189f 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -7055,7 +7055,7 @@ grokdeclarator (const struct c_declarator *declarator,
"returning a function");
type = integer_type_node;
}
- if (TREE_CODE (type) == ARRAY_TYPE)
+ if (TREE_CODE (type) == ARRAY_TYPE && !flag_array_copy)
{
if (name)
error_at (loc, "%qE declared as function returning an array",
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 4ee21c7bdbd..c73fb73d86e 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -908,29 +908,34 @@ static bool
can_convert_array (tree atype, tree from, int flags, tsubst_flags_t complain)
{
tree elttype = TREE_TYPE (atype);
- unsigned i;
if (TREE_CODE (from) == CONSTRUCTOR)
{
- for (i = 0; i < CONSTRUCTOR_NELTS (from); ++i)
+ for (auto&& ce : CONSTRUCTOR_ELTS (from))
{
- tree val = CONSTRUCTOR_ELT (from, i)->value;
- bool ok;
- if (TREE_CODE (elttype) == ARRAY_TYPE)
- ok = can_convert_array (elttype, val, flags, complain)
