digitalmars.D.bugs - [Issue 7444] New: Require [] for array copies too
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http://d.puremagic.com/issues/show_bug.cgi?id=7444
Summary: Require [] for array copies too
Product: D
Version: D2
Platform: All
OS/Version: All
Status: NEW
Severity: enhancement
Priority: P2
Component: DMD
AssignedTo: nobody puremagic.com
ReportedBy: bearophile_hugs eml.cc
This is derived from issue 3971 see there for more (messy) discussions.
In 2.058 this compiles:
int[100] foo() {
int[100] a;
return a;
}
void main() {
int[10_000] a, b;
auto c = new int[10_000];
a = 1;
a = b;
a = c;
auto d = foo();
}
But for consistency of the vector ops syntax, and to help the programmer spot
where the code is doing a potentially long copy, I suggest to turn that first
program into a compile-time error, and require [] on lvalues everywhere you
perform a vector operation, like when you copy a int[N] on another int[N], etc:
int[100] foo() {
int[100] a;
return a;
}
void main() {
int[10_000] a, b;
auto c = new int[10_000];
a[] = 1;
a[] = b;
a[] = c;
auto d[] = foo(); // currently an error
}
- - - - - - - - - - - - - - - -
But note that normally all array ops require a [] even on the rvalue:
void main() {
int[10_000] a, b;
a[] += b[];
}
So an alternative stricter proposal is to require [] on the right too:
int[100] foo() {
int[100] a;
return a;
}
void main() {
int[10_000] a, b;
auto c = new int[10_000];
auto d = new int[10_000];
a[] = 1;
a[] = b[];
a[] = c[];
c[] = d[];
auto e[] = foo()[]; // currently an error
}
It helps the programmer tell apart two different cases, that currently are
usable with the same syntax (from an example by Don):
void main() {
int[][3] x;
int[] y;
int[] z;
x[] = z; // copies just the z pointer
y[] = z; // copies the elements in z
}
Requiring [] on the right (rvalue) for the copy of many items avoids the
ambiguity:
void main() {
int[][3] x;
int[] y;
int[] z;
x[] = z;
y[] = z[];
}
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Feb 05 2012
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=7444
timon.gehr gmx.ch changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |timon.gehr gmx.ch
While I agree that the syntax should be enforced more strictly in general, I
still completely disagree with requiring [] on static array copies. Static
arrays are value types of fixed size, and should be treated as such. Requiring
[] is just wrong.
void foo(int[4] x){}
void foo(int[] y){}
void main(){
int[4] x, y;
struct S{int[4] x;}
S a, b;
x = y;
a = b; // why should this work if the above does not?
foo(x); // copies, you want this to be an error
foo(x[]); // calls the other overload, does not copy
}
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Feb 05 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444
While I agree that the syntax should be enforced more strictly in general, I
still completely disagree with requiring [] on static array copies. Static
arrays are value types of fixed size, and should be treated as such. Requiring
[] is just wrong.
void foo(int[4] x){}
void foo(int[] y){}
void main(){
int[4] x, y;
struct S{int[4] x;}
S a, b;
x = y;
a = b; // why should this work if the above does not?
foo(x); // copies, you want this to be an error
foo(x[]); // calls the other overload, does not copy
}
I completely agree with Timon.
When x and y are declared with same type T, x = y is identity assignment, and
it is valid syntax even if T is static array type.
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Feb 09 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444
I'd like to provide an exhaustive test that should compile after fixing the
enhancement suggested by me and timon.
----
// X: Changed accepts-invalid to rejects-invalid by this issue
// a: slice assginment
// b: element-wise assignment
static assert(!__traits(compiles, { sa = e; })); // X
static assert( __traits(compiles, { sa[] = e; })); // b
static assert(!__traits(compiles, { da = e; }));
static assert( __traits(compiles, { da[] = e; })); // b
// lhs is static array
static assert( __traits(compiles, { sa = sa; })); // b == identity assign
static assert(!__traits(compiles, { sa = sa[]; })); // X
static assert(!__traits(compiles, { sa[] = sa; })); // X
static assert( __traits(compiles, { sa[] = sa[]; })); // b
static assert(!__traits(compiles, { sa = da; })); // X
static assert(!__traits(compiles, { sa = da[]; })); // X
static assert( __traits(compiles, { sa[] = da; })); // b
static assert( __traits(compiles, { sa[] = da[]; })); // b
// lhs is dynamic array
static assert(!__traits(compiles, { da = sa; })); // X
static assert( __traits(compiles, { da = sa[]; })); // a
static assert(!__traits(compiles, { da[] = sa; })); // X
static assert( __traits(compiles, { da[] = sa[]; })); // b
static assert( __traits(compiles, { da = da; })); // a == identity assign
static assert( __traits(compiles, { da = da[]; })); // a
static assert( __traits(compiles, { da[] = da; })); // b
static assert( __traits(compiles, { da[] = da[]; })); // b
----
bearophile says that sa = sa should be rejected and must replace it to sa[] =
sa[].
But I and timon disagree it.
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Feb 09 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444 Maybe sa[] = da and da[] = da should be '// X' too. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Feb 09 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444
Kenji Hara <k.hara.pg gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |pull
Maybe sa[] = da and da[] = da should be '// X' too.
Hmm, OK. If it is an element-wise assignment, we should add explicit slicing
both side of AssignExp.
I've posted a pull to implement this enhancement:
https://github.com/D-Programming-Language/dmd/pull/702
Updated test:
https://github.com/D-Programming-Language/dmd/pull/702/files#L6R250
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Feb 10 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444
Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |bugzilla digitalmars.com
23:27:14 PST ---
The enhancement is to disallow:
sa = da; // use sa[] = da[] instead
sa = e; // use sa[] = e instead
I'm not sure this is worth the existing code breakage.
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Feb 17 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444I'm not sure this is worth the existing code breakage.I thin it's worth it, if you want with warning / deprecation / error stages. But if want, I'll ask for a little voting in the main D newsgroup. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Feb 18 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444 See why a consistent syntax matters: Issue 7564 -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Feb 22 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444 Commits pushed to master at https://github.com/D-Programming-Language/druntime https://github.com/D-Programming-Language/druntime/commit/a77c82772e7e7b2d1d863b1fb56b614b9d4bc6a1 fix Issue 7444 - Require [] for array copies too https://github.com/D-Programming-Language/druntime/commit/be3a7fa1bc726b453203c058ff2fa8c81dcfcab1 Supplemental changes for Issue 7444 - Require [] for array copies too -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Oct 14 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444 Commits pushed to master at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/28dedee456e741f02f08a944f41daa9e46236224 Issue 7444 - Require [] for array copies too https://github.com/D-Programming-Language/phobos/commit/9a6dad8a2ac5841bdcfa2b86082450818f6eefab Supplemental changes for Issue 7444 - Require [] for array copies too -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Nov 20 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444 Commits pushed to master at https://github.com/D-Programming-Language/druntime https://github.com/D-Programming-Language/druntime/commit/e5895640c83d8b5b4c8b2404b4e639ba6fdf2243 Additional fix Issue 7444 in Posix platforms https://github.com/D-Programming-Language/druntime/commit/a54f41c98aa26eeb70274e8b78d8abfb575bcebc Additional fix Issue 7444 in Posix platforms -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Nov 21 2012
http://d.puremagic.com/issues/show_bug.cgi?id=7444 Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/57b770ed49379c5af726d23356e0f75818a3f859 Issue 7444 - Require [] for array copies too https://github.com/D-Programming-Language/dmd/commit/ba1009c5561b51b8f18d9c869fde9bd45cb7ebc7 Issue 7444 - Require [] for array copies too -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 06 2013
http://d.puremagic.com/issues/show_bug.cgi?id=7444Commits pushed to master at https://github.com/D-Programming-Language/dmd https://github.com/D-Programming-Language/dmd/commit/57b770ed49379c5af726d23356e0f75818a3f859 Issue 7444 - Require [] for array copies too https://github.com/D-Programming-Language/dmd/commit/ba1009c5561b51b8f18d9c869fde9bd45cb7ebc7 Issue 7444 - Require [] for array copies tooI have tried this change, and now the first test case of this ER: int[100] foo() { int[100] a; return a; } void main() { int[10_000] a, b; auto c = new int[10_000]; a = 1; a = b; a = c; auto d = foo(); } gives a ICE: temp.d(8): Warning: explicit element-wise assignment (a)[] = 1 is better than a = 1 temp.d(10): Warning: explicit element-wise assignment (a)[] = (c)[] is better than a = c Assertion failure: '0' on line 1193 in file 'glue.c' -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 07 2013
http://d.puremagic.com/issues/show_bug.cgi?id=7444gives a ICE:Smaller test case: void main() { int[1] a; a = 1; } -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 07 2013
http://d.puremagic.com/issues/show_bug.cgi?id=7444 ---What version and compiler switch do you use? I cannot reproduce the ICE. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------gives a ICE:Smaller test case: void main() { int[1] a; a = 1; }
Mar 07 2013
http://d.puremagic.com/issues/show_bug.cgi?id=7444What version and compiler switch do you use? I cannot reproduce the ICE.I am using the GIT head compiler, I have downloaded and compiled dmd few hours ago, after this patch was merged. I am on Windows 32 bit, and I have compiled the code with: dmd -wi test.d -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 07 2013
http://d.puremagic.com/issues/show_bug.cgi?id=7444 ---Thanks. -w option does not reproduce it, but -wi does. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------What version and compiler switch do you use? I cannot reproduce the ICE.I am using the GIT head compiler, I have downloaded and compiled dmd few hours ago, after this patch was merged. I am on Windows 32 bit, and I have compiled the code with: dmd -wi test.d
Mar 07 2013
http://d.puremagic.com/issues/show_bug.cgi?id=7444
Kenji Hara <k.hara.pg gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
---
What version and compiler switch do you use? I cannot reproduce the ICE.
I am using the GIT head compiler, I have downloaded and compiled dmd few hours
ago, after this patch was merged.
I am on Windows 32 bit, and I have compiled the code with:
dmd -wi test.d
Thanks. -w option does not reproduce it, but -wi does.
OK, I opened a new report bug 9663 for the regression.
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Mar 07 2013
http://d.puremagic.com/issues/show_bug.cgi?id=7444
Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|FIXED |WONTFIX
09:38:57 PDT ---
This pull:
https://github.com/D-Programming-Language/dmd/pull/2673
undoes it with explanation. Reclassified as "wontfix".
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Oct 20 2013
http://d.puremagic.com/issues/show_bug.cgi?id=7444This pull: https://github.com/D-Programming-Language/dmd/pull/2673 undoes it with explanation. Reclassified as "wontfix".What? After all the energy time and work spent on fixing this problem!? If you take a look at the patch by Kenji you see: - else if (global.params.warnings && !global.gag && op == TOKassign && + else if (0 && global.params.warnings && !global.gag && op == TOKassign && That means the code is commented out, but it's meant to be activated back in dmd 2.065 to try to fix this issue better. I will probably re-open this issue later. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Oct 20 2013
http://d.puremagic.com/issues/show_bug.cgi?id=7444
bearophile_hugs eml.cc changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|WONTFIX |
Reopened, this will wait for dmd 2.065, to see if Kenji or others are able to
find a solution. If no solution will be found, we'll close this again.
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Oct 20 2013