RE: [sv-bc] "Assignment ... to a constant expression"

That was the original intent. That sentence comes from 1364-2001, 6.2.1:

"The variable declaration assignment is a special case of procedural
assignment as it assigns a value to a variable. It allows an initial
value to be placed in a variable in the same statement that declares the
variable. The assignment shall be to a constant expression. The
assignment does not have duration; instead, the variable holds the value
until the next assignment to that variable. Variable declaration
assignments to an array are not allowed. Variable declaration
assignments are only allowed at the module level."

Note that in the BNF, originally when the variable declaration
assignment was introduced in Verilog-2001, the RHS was
constant_expression. In SV 3.1a, it was changed from constant_expression
to expression, to allow expressions that constant_expression does not
allow.

While the use of "to" here is misleading, as the assignment is to the
variable, not to the RHS, the entire sentence is no longer correct. 6.7
says,

"A variable can be declared with an initializer, for example: int i = 0;
..
Initial values are not constrained to simple constants; they can include
run-time expressions, including dynamic memory allocation. For example,
a static class handle or a mailbox can be created and initialized by
calling its new method (see 15.4.1), or static variables can be
initialized to random values by calling the $urandom system task. This
may require a special pre-initial pass at run time."

That is what happens when a single subject is described in several
places. Besides correcting 10.5, the two sub-clauses should
cross-reference each other. Even better would be to merge them.

As an LRM merge issue, I believe we can still work on this.

Thanks,
Shalom


> According to 10.5 of Draft 4 --
> 
>   "The variable declaration assignment is a special case of 
> procedural assignment as it assigns a value to a variable. It 
> allows an initial value to be placed in a variable in the 
> same statement that declares the variable. The assignment 
> shall be to a constant expression."
> 
> What does it mean to assign "to a constant expression"?  Is 
> this trying to say that in a variable_decl_assignment, if the 
> variable is static, then the right-hand side shall be a 
> constant expression?
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