digitalmars.D - Immutable cannot be casted to const when using pointers
- Jeroen Bollen (31/31) Apr 08 2014 For some reason this code doesn't work...
- John Colvin (2/33) Apr 08 2014 Looks like a bug to me.
- Jeroen Bollen (2/46) Apr 08 2014 Alright, filing it.
- Jeroen Bollen (1/1) Apr 08 2014 Here we go: https://d.puremagic.com/issues/show_bug.cgi?id=12549
- Peter Alexander (10/11) Apr 08 2014 Not a bug:
- =?UTF-8?B?QWxpIMOHZWhyZWxp?= (4/7) Apr 08 2014 Yeah. A known issue in C and C++ as well:
- Artur Skawina (6/25) Apr 08 2014 void test2(const(char)** test2) {
- Steven Schveighoffer (8/22) Apr 08 2014 ...
- Jeroen Bollen (6/9) Apr 09 2014 For some reason I was expecting that to rhyme. :P
- Steven Schveighoffer (8/17) Apr 10 2014 Without knowing more information, it's hard to say.
For some reason this code doesn't work...
module app;
void main() {
immutable char var = 'a';
immutable(char)* varPtr = &var;
test(&varPtr);
}
void test(immutable(char)** param) {
test2(param);
}
void test2(const(char)** test2) {
}
It'll give you " Error: function app.test2 (const(char)** test2)
is not callable using argument types (immutable(char)**)", which
makes no sense as if a function requests a constant variable,
immutable should suffice.
What's even weirder (although it is what should happen), if you
remove one of the pointers, it compiles fine.
module app;
void main() {
immutable char var = 'a';
test(&var);
}
void test(immutable(char)* param) {
test2(param);
}
void test2(const(char)* test2) {
}
Is this a bug? I'm using DMD.
Apr 08 2014
On Tuesday, 8 April 2014 at 21:05:10 UTC, Jeroen Bollen wrote:
For some reason this code doesn't work...
module app;
void main() {
immutable char var = 'a';
immutable(char)* varPtr = &var;
test(&varPtr);
}
void test(immutable(char)** param) {
test2(param);
}
void test2(const(char)** test2) {
}
It'll give you " Error: function app.test2 (const(char)**
test2) is not callable using argument types
(immutable(char)**)", which makes no sense as if a function
requests a constant variable, immutable should suffice.
What's even weirder (although it is what should happen), if you
remove one of the pointers, it compiles fine.
module app;
void main() {
immutable char var = 'a';
test(&var);
}
void test(immutable(char)* param) {
test2(param);
}
void test2(const(char)* test2) {
}
Is this a bug? I'm using DMD.
Looks like a bug to me.
Apr 08 2014
On Tuesday, 8 April 2014 at 21:07:29 UTC, John Colvin wrote:On Tuesday, 8 April 2014 at 21:05:10 UTC, Jeroen Bollen wrote:Alright, filing it.For some reason this code doesn't work... module app; void main() { immutable char var = 'a'; immutable(char)* varPtr = &var; test(&varPtr); } void test(immutable(char)** param) { test2(param); } void test2(const(char)** test2) { } It'll give you " Error: function app.test2 (const(char)** test2) is not callable using argument types (immutable(char)**)", which makes no sense as if a function requests a constant variable, immutable should suffice. What's even weirder (although it is what should happen), if you remove one of the pointers, it compiles fine. module app; void main() { immutable char var = 'a'; test(&var); } void test(immutable(char)* param) { test2(param); } void test2(const(char)* test2) { } Is this a bug? I'm using DMD.Looks like a bug to me.
Apr 08 2014
Here we go: https://d.puremagic.com/issues/show_bug.cgi?id=12549
Apr 08 2014
On Tuesday, 8 April 2014 at 21:13:47 UTC, Jeroen Bollen wrote:Here we go: https://d.puremagic.com/issues/show_bug.cgi?id=12549Not a bug: What you are asking for is to allow immutable(T)** and int** to convert to const(T)** int a = 0; int* pa = &a; const(int)** ppa = &pa; // not currently allowed immutable(int) b = 1; *ppa = &b; // equivalent to pa = &b!!! i.e. pa (mutable) now points at b (immutable)!!!
Apr 08 2014
=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> On 04/08/2014 02:38 PM, Peter Alexander wrote:On Tuesday, 8 April 2014 at 21:13:47 UTC, Jeroen Bollen wrote:Yeah. A known issue in C and C++ as well: http://www.parashift.com/c++-faq/constptrptr-conversion.html AliHere we go: https://d.puremagic.com/issues/show_bug.cgi?id=12549Not a bug:
Apr 08 2014
On 04/08/14 23:05, Jeroen Bollen wrote:
For some reason this code doesn't work...
module app;
void main() {
immutable char var = 'a';
immutable(char)* varPtr = &var;
test(&varPtr);
}
void test(immutable(char)** param) {
test2(param);
}
void test2(const(char)** test2) {
}
It'll give you " Error: function app.test2 (const(char)** test2) is not
callable using argument types (immutable(char)**)", which makes no sense as if
a function requests a constant variable, immutable should suffice.
void test2(const(char)** test2) {
static char b = 'b';
*test2 = &b;
}
artur
Apr 08 2014
On Tue, 08 Apr 2014 17:05:09 -0400, Jeroen Bollen <jbinero gmail.com> wrote:For some reason this code doesn't work... module app; void main() { immutable char var = 'a'; immutable(char)* varPtr = &var; test(&varPtr); } void test(immutable(char)** param) { test2(param); } void test2(const(char)** test2) { }...Is this a bug? I'm using DMD.No, it's intended. If that was allowed, you could inadvertently overwrite immutable data without a cast. The rule of thumb is, 2 or more references deep does not implicitly convert. One reference deep is OK. -Steve
Apr 08 2014
On Tuesday, 8 April 2014 at 21:53:58 UTC, Steven Schveighoffer wrote:The rule of thumb is, 2 or more references deep does not implicitly convert. One reference deep is OK. -SteveFor some reason I was expecting that to rhyme. :P Anyways thanks all, makes sense now. Are there any workarounds? The function taking the const int** is external(C) so I'm not sure what to do.
Apr 09 2014
On Wed, 09 Apr 2014 06:25:34 -0400, Jeroen Bollen <jbinero gmail.com> wrote:On Tuesday, 8 April 2014 at 21:53:58 UTC, Steven Schveighoffer wrote:Without knowing more information, it's hard to say. You can create a temporary: // immutable(char)** v const(char)* x = *v; foo(&x); -SteveThe rule of thumb is, 2 or more references deep does not implicitly convert. One reference deep is OK. -SteveFor some reason I was expecting that to rhyme. :P Anyways thanks all, makes sense now. Are there any workarounds? The function taking the const int** is external(C) so I'm not sure what to do.
Apr 10 2014