2 Oct
2015
2 Oct
'15
9:38 a.m.
On 01/10/15 14:34, Sven Neuhaus wrote:
Why? Do you know the purpose of parameters for C libc functions without
fist looking at the manual? One needs to retrieve values, so instead of
evaluating the value, is about setting the value.
That's pretty much from day 0 of sip express router back in 2001 -- the
parameters of functions from modules had to be enclosed in double
quotes, not matter what they are. There was no support for expressions
as parameters for functions. Later there were some changes and some
parameters can be without double quotes, but that is not the general
rule -- if in double quotes, it should work always (for module functions).
Cheers,
Daniel
--
Daniel-Constantin Mierla
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Am 01.10.2015 um 12:53 schrieb Daniel-Constantin
Mierla:
In C is not :-) .
there are different actions, one is assignment of
an expression and the
other is a function call. Functions can evaluate they parameters as they
need/want by having the appropriate C code inside.
After I noticed the problem and
tried to understand what was going on,
that's what I came up with. That doesn't make it less error prone, however.
For assignments, that is the general interpreter
which considers strings
as being the tokens in between quotes. Trying to interpret variables
inside the strings automatically won't work, because that will mean to
do it for cases when it should not happen (e.g., modparams or function
parameters that specify just name of variables). Of course, with some
extra coding to keep states of where that string is used might be
possible, but I think will make the interpreter too complex. I might be
wrong, so a patch is welcome to prove the otherwise :-)
Ideally, all variables in
double quoted strings should be interpolated
and single quoted strings should not (the same way it is done in bash,
Perl, PHP, Groove, Ruby and elsewhere). Some functions can evaluate the parameter
content, some don't. And in
some cases, even there is a variable inside a parameter for a function,
it is not evaluated, but it is set. That's again based on the purpose of
the function.
That's frightening! Instead of concatenation expression, you can use
few other options:
- $_s(...) -- iirc, like:
That $_() is a useful thing to know.
$var(x) =
$_s("sip:+$var(abc)-$var(def)-$si@$Ri:$Rp");
- pv_printf($var(x), ...)
I looked up the documentation for pv_printf() in the KEx
module and was
baffled to see the variable name being passed as a string in the example
... "pv_printf("$ru", "sip:$rU@$fd");" :-*