chapelu
September 3, 2024, 6:30pm
1
25858, "ty1027", "[Bug]: 'const' attached to vararg formal arguments allows their modification", "2024-09-03T18:28:40Z"
opened 06:28PM - 03 Sep 24 UTC
closed 02:34PM - 04 Sep 24 UTC
type: Bug
user issue
### Summary of Problem
**Description:**
The following code receives multip… le arguments as a tuple (`args`) and attempts to modify
the 1st element of the tuple. ([ATO](https://ato.pxeger.com/run?1=ZZBNDoIwEIXjxkVPMWFFCZYfN0bCHdwbF4gtkgBtyhBDjCdxw0YP5Wks_hFwVpN537zJvOs9PSaKF113a1AsVo_Z3PNAaZlC2W50XmFR2YnOasYYBSPZTkDJRE9lVSOMqZCSMwE46Ry5QayXiq3i0FcMlgu_0bpG45TRaLoA9p4LqTkdFgxkqL7b-jtwYgj8CPqTpTzkogVsVMHJv1EikOuxz4WQ4YfAhZAtXbCEbLRFo3ccn1S-6TwB))
```chapel
// proc myPrintln(args...) // (*1)
proc myPrintln(const args...) // (*2)
{
writeln("args.type = ", args.type:string);
writeln("args (before) = ", args);
args[0] *= 10; // modify tuple (just for test)
writeln("args (after) = ", args);
}
myPrintln(1, 2.3, "four");
```
With no `const` attached (as in Line (*1)), the code prints
```
args (after) = (10, 2.3, four)
```
as expected. On the other hand, if I attach `const` to `args` (as in Line (*2)),
the code still prints the same result, so allowing the modification of `args`.
I posted the above code in the Chapel Discourse (in this [thread](https://chapel.discourse.group/t/const-attached-to-vararg-formal-argument/36578)), and Brad suggests that it may be a compiler bug
(based on another example code for tuples). Please take a look at the above
Discourse page for Brad's test code and explanations.
**Is this issue currently blocking your progress?**
No. (I happened to observe this behavior when playing with `vararg` for practice).
### Steps to Reproduce
I tested the code with the above ATO site.
Description:
The following code receives multiple arguments as a tuple (args) and attempts to modifyATO )
// proc myPrintln(args...) // (*1)
proc myPrintln(const args...) // (*2)
{
writeln("args.type = ", args.type:string);
writeln("args (before) = ", args);
args[0] *= 10; // modify tuple (just for test)
writeln("args (after) = ", args);
}
myPrintln(1, 2.3, "four");
With no const attached (as in Line (*1)), the code prints
args (after) = (10, 2.3, four)
as expected. On the other hand, if I attach const to args (as in Line (*2)),args.
I posted the above code in the Chapel Discourse (in this thread ), and Brad suggests that it may be a compiler bug
Is this issue currently blocking your progress? vararg for practice).
I tested the code with the above ATO site.