Re: Can we check the arguments to format() at compile time?

[Andrei Alexandrescu via Digitalmars-d]

On 04/01/2016 07:26 PM, Alex Parrill wrote:

On Friday, 1 April 2016 at 21:25:46 UTC, Yuxuan Shui wrote:

Clang has this nice feature that it will warn you when you passed
wrong arguments to printf:

#include 
int main(){
long long u = 10;
printf("%c", u);
}

clang something.c:
something.c:4:15: warning: format specifies type 'int' but the
argument has type 'long long' [-Wformat]

With the CTFE power of D, we should be able to do the same thing when
the format string is available at compile time. Instead of throwing
exceptions at run time.


Not as-is, because the format string is a runtime argument and not a
compile-time constant.

Consider:

 writefln(rand() >= 0.5 ? "%s" : "%d", 123);

It's certainly possible with a new, templated writef function.
Hypothetically:

 writefln_ctfe!"%s"(1234); // would fail


What happened to the work that added a compile-time string to writef? -- 
Andrei

Re: Can we check the arguments to format() at compile time?

[Johan Engelen via Digitalmars-d]

On Friday, 1 April 2016 at 21:25:46 UTC, Yuxuan Shui wrote:
Clang has this nice feature that it will warn you when you 
passed wrong arguments to printf:


#include 
int main(){
long long u = 10;
printf("%c", u);
}

clang something.c:
something.c:4:15: warning: format specifies type 'int' but the 
argument has type 'long long' [-Wformat]


With the CTFE power of D, we should be able to do the same 
thing when the format string is available at compile time. 
Instead of throwing exceptions at run time.


I thought LDC already did that when `-check-printf-calls` is 
passed, but the implementation is unfinished and it does not do 
any checking at the moment.

Re: Can we check the arguments to format() at compile time?

[Jacob Carlborg via Digitalmars-d]

On 2016-04-02 01:40, Yuxuan Shui wrote:


That's kind of ugly. Now I really wish D can unify template arguments
and function arguments known at compile time.


Sounds like AST macros.

--
/Jacob Carlborg

Re: Can we check the arguments to format() at compile time?

[Daniel Murphy via Digitalmars-d]

On 2/04/2016 8:25 AM, Yuxuan Shui wrote:

Clang has this nice feature that it will warn you when you passed wrong
arguments to printf:

#include 
int main(){
 long long u = 10;
 printf("%c", u);
}

clang something.c:
something.c:4:15: warning: format specifies type 'int' but the argument
has type 'long long' [-Wformat]

With the CTFE power of D, we should be able to do the same thing when
the format string is available at compile time. Instead of throwing
exceptions at run time.


That's something I want to do with this eventually: 
https://github.com/D-Programming-Language/dmd/pull/3799


When arguments (or anything about the arguments) is known at compile 
time, some subsets of in-contracts can be checked.


Currently only stuff like this is supported:
auto iota(int low, int high) in { assert(low <= high); } body { ... }

iota(23, 7); // Error

But it's not impossible that
assert(checkFormatArgs(format, args));
could work one day.

Re: Can we check the arguments to format() at compile time?

[Yuxuan Shui via Digitalmars-d]

On Friday, 1 April 2016 at 23:26:14 UTC, Alex Parrill wrote:

On Friday, 1 April 2016 at 21:25:46 UTC, Yuxuan Shui wrote:

[...]


Not as-is, because the format string is a runtime argument and 
not a compile-time constant.


Consider:

writefln(rand() >= 0.5 ? "%s" : "%d", 123);

It's certainly possible with a new, templated writef function. 
Hypothetically:


writefln_ctfe!"%s"(1234); // would fail


That's kind of ugly. Now I really wish D can unify template 
arguments and function arguments known at compile time.

Re: Can we check the arguments to format() at compile time?

[Alex Parrill via Digitalmars-d]

On Friday, 1 April 2016 at 21:25:46 UTC, Yuxuan Shui wrote:
Clang has this nice feature that it will warn you when you 
passed wrong arguments to printf:


#include 
int main(){
long long u = 10;
printf("%c", u);
}

clang something.c:
something.c:4:15: warning: format specifies type 'int' but the 
argument has type 'long long' [-Wformat]


With the CTFE power of D, we should be able to do the same 
thing when the format string is available at compile time. 
Instead of throwing exceptions at run time.


Not as-is, because the format string is a runtime argument and 
not a compile-time constant.


Consider:

writefln(rand() >= 0.5 ? "%s" : "%d", 123);

It's certainly possible with a new, templated writef function. 
Hypothetically:


writefln_ctfe!"%s"(1234); // would fail

Can we check the arguments to format() at compile time?

[Yuxuan Shui via Digitalmars-d]

Clang has this nice feature that it will warn you when you passed 
wrong arguments to printf:


#include 
int main(){
long long u = 10;
printf("%c", u);
}

clang something.c:
something.c:4:15: warning: format specifies type 'int' but the 
argument has type 'long long' [-Wformat]


With the CTFE power of D, we should be able to do the same thing 
when the format string is available at compile time. Instead of 
throwing exceptions at run time.