string file = __FILE__ considered harmful (and solution)
There's a very common idiom where in order to report line numbers
of an error or a log line at the callsite of a function, you pass
__FILE__ and __LINE__ as default parameters:
void foo(string file = __FILE__, size_t line = __LINE__);
What's wrong with this?
Say you add a string parameter, such as
void foo(string msg, string file = __FILE__, size_t line =
__LINE__);
foo("Hello World");
Now when you accidentally grab an old version of the library,
your new code will still run, but it will believe that it's being
called from file "Hello World", line 15. Not good.
Luckily there's a fix. Just stick this in some common header file
in your project:
struct CallerInfo
{
string file;
size_t line;
}
void foo(string msg, CallerInfo caller = CallerInfo(__FILE__,
__LINE__));
Now you cannot accidentally invoke foo with a string, or in fact
any type except another instance of CallerInfo.
This is such a basic type that it really belongs in phobos,
arguably object.d. At which point we can shorten this to
CallerInfo caller = __CALLER__, and be forward compatible for
additional information about the callsite, such as, say,
attributes of the calling function.
Re: string file = __FILE__ considered harmful (and solution)
On 30/05/2018 8:27 PM, FeepingCreature wrote:
There's a very common idiom where in order to report line numbers of an
error or a log line at the callsite of a function, you pass __FILE__ and
__LINE__ as default parameters:
void foo(string file = __FILE__, size_t line = __LINE__);
What's wrong with this?
Say you add a string parameter, such as
void foo(string msg, string file = __FILE__, size_t line = __LINE__);
foo("Hello World");
Now when you accidentally grab an old version of the library, your new
code will still run, but it will believe that it's being called from
file "Hello World", line 15. Not good.
Luckily there's a fix. Just stick this in some common header file in
your project:
struct CallerInfo
{
string file;
size_t line;
}
void foo(string msg, CallerInfo caller = CallerInfo(__FILE__, __LINE__));
Now you cannot accidentally invoke foo with a string, or in fact any
type except another instance of CallerInfo.
This is such a basic type that it really belongs in phobos, arguably
object.d. At which point we can shorten this to CallerInfo caller =
__CALLER__, and be forward compatible for additional information about
the callsite, such as, say, attributes of the calling function.
ooo I have another solution.
Use a named argument[0]!
[0] https://github.com/rikkimax/DIPs/blob/named_args/DIPs/DIP1xxx-RC.md
Re: string file = __FILE__ considered harmful (and solution)
Shit it doesn't work, I only checked if it compiled; it gives the wrong file/line number. NEVERMIND ALL
Re: string file = __FILE__ considered harmful (and solution)
On Wednesday, 30 May 2018 at 08:27:16 UTC, FeepingCreature wrote: There's a very common idiom where in order to report line numbers of an error or a log line at the callsite of a function, you pass __FILE__ and __LINE__ as default parameters: [...] void foo(string file = __FILE__, size_t line = __LINE__)(string msg); Wouldn't this solve it?
Re: string file = __FILE__ considered harmful (and solution)
On Wednesday, 30 May 2018 at 11:59:05 UTC, bauss wrote: On Wednesday, 30 May 2018 at 08:27:16 UTC, FeepingCreature wrote: There's a very common idiom where in order to report line numbers of an error or a log line at the callsite of a function, you pass __FILE__ and __LINE__ as default parameters: [...] void foo(string file = __FILE__, size_t line = __LINE__)(string msg); Wouldn't this solve it? No, because a) then you're completely pointlessly making a foo for every line it's called in, b) you're not future compatible with, say, call column, and c) you get exactly the same problem with template value parameters, ie. foo!"some ct argument".
Re: string file = __FILE__ considered harmful (and solution)
On 5/30/18 4:27 AM, FeepingCreature wrote:
There's a very common idiom where in order to report line numbers of an
error or a log line at the callsite of a function, you pass __FILE__ and
__LINE__ as default parameters:
void foo(string file = __FILE__, size_t line = __LINE__);
What's wrong with this?
Say you add a string parameter, such as
void foo(string msg, string file = __FILE__, size_t line = __LINE__);
foo("Hello World");
Now when you accidentally grab an old version of the library, your new
code will still run, but it will believe that it's being called from
file "Hello World", line 15. Not good.
Luckily there's a fix. Just stick this in some common header file in
your project:
struct CallerInfo
{
string file;
size_t line;
}
void foo(string msg, CallerInfo caller = CallerInfo(__FILE__, __LINE__));
Now you cannot accidentally invoke foo with a string, or in fact any
type except another instance of CallerInfo.
Awesome idea! Unfortunately, it doesn't work. The __FILE__ and __LINE__
there are not from the caller, but from the line that defines foo.
See here: https://run.dlang.io/is/siz9YZ
At which point we can shorten this to CallerInfo caller =
__CALLER__, and be forward compatible for additional information about
the callsite, such as, say, attributes of the calling function.
Hm.. I don't like this too much. Adding more magic to the compiler seems
unnecessary.
But if we fixed the behavior that causes your idea not to work, then we
could probably easily define a function like so:
CallerInfo __CALLER__(string file = __FILE__, size_t line = __LINE__)
{
return CallerInfo(file, line);
}
-Steve
Re: string file = __FILE__ considered harmful (and solution)
On 5/30/18 10:40 AM, Steven Schveighoffer wrote:
But if we fixed the behavior that causes your idea not to work, then we
could probably easily define a function like so:
CallerInfo __CALLER__(string file = __FILE__, size_t line = __LINE__)
{
return CallerInfo(file, line);
}
Filed an issue so it's not forgotten:
https://issues.dlang.org/show_bug.cgi?id=18919
-Steve
Re: string file = __FILE__ considered harmful (and solution)
On 05/30/2018 10:40 AM, Steven Schveighoffer wrote:
But if we fixed the behavior that causes your idea not to work, then we
could probably easily define a function like so:
CallerInfo __CALLER__(string file = __FILE__, size_t line = __LINE__)
{
return CallerInfo(file, line);
}
Love it!
Re: string file = __FILE__ considered harmful (and solution)
On Wednesday, 30 May 2018 at 14:40:50 UTC, Steven Schveighoffer
wrote:
On 5/30/18 4:27 AM, FeepingCreature wrote:
There's a very common idiom where in order to report line
numbers of an error or a log line at the callsite of a
function, you pass __FILE__ and __LINE__ as default parameters:
void foo(string file = __FILE__, size_t line = __LINE__);
What's wrong with this?
Say you add a string parameter, such as
void foo(string msg, string file = __FILE__, size_t line =
__LINE__);
foo("Hello World");
Now when you accidentally grab an old version of the library,
your new code will still run, but it will believe that it's
being called from file "Hello World", line 15. Not good.
Luckily there's a fix. Just stick this in some common header
file in your project:
struct CallerInfo
{
string file;
size_t line;
}
void foo(string msg, CallerInfo caller = CallerInfo(__FILE__,
__LINE__));
Now you cannot accidentally invoke foo with a string, or in
fact any type except another instance of CallerInfo.
Awesome idea! Unfortunately, it doesn't work. The __FILE__ and
__LINE__ there are not from the caller, but from the line that
defines foo.
See here: https://run.dlang.io/is/siz9YZ
https://run.dlang.io/is/oMe7KQ
Less elegant, but solves the problem of accidental argument
adding (CallerFile acts as a barrier). Unfortunately, while it
works in theory, in practice the compiler crashes LOL
Re: string file = __FILE__ considered harmful (and solution)
On Wednesday, 30 May 2018 at 14:40:50 UTC, Steven Schveighoffer
wrote:
On 5/30/18 4:27 AM, FeepingCreature wrote:
There's a very common idiom where in order to report line
numbers of an error or a log line at the callsite of a
function, you pass __FILE__ and __LINE__ as default parameters:
void foo(string file = __FILE__, size_t line = __LINE__);
What's wrong with this?
Say you add a string parameter, such as
void foo(string msg, string file = __FILE__, size_t line =
__LINE__);
foo("Hello World");
Now when you accidentally grab an old version of the library,
your new code will still run, but it will believe that it's
being called from file "Hello World", line 15. Not good.
Luckily there's a fix. Just stick this in some common header
file in your project:
struct CallerInfo
{
string file;
size_t line;
}
void foo(string msg, CallerInfo caller = CallerInfo(__FILE__,
__LINE__));
Now you cannot accidentally invoke foo with a string, or in
fact any type except another instance of CallerInfo.
Awesome idea! Unfortunately, it doesn't work. The __FILE__ and
__LINE__ there are not from the caller, but from the line that
defines foo.
See here: https://run.dlang.io/is/siz9YZ
At which point we can shorten this to CallerInfo caller =
__CALLER__, and be forward compatible for additional
information about the callsite, such as, say, attributes of
the calling function.
Hm.. I don't like this too much. Adding more magic to the
compiler seems unnecessary.
But if we fixed the behavior that causes your idea not to work,
then we could probably easily define a function like so:
CallerInfo __CALLER__(string file = __FILE__, size_t line =
__LINE__)
{
return CallerInfo(file, line);
}
-Steve
Instead of these hack keywords.
Perhaps a __traits() in the compiler with the information would
be better suited like:
void foo()
{
enum caller = __traits(getCaller);
}
getCaller would return a compile-time struct with additional
information about the current module and the module/function it
was called from.
Alternatively you can use the following traits.
true/false as secondary argument for whether it should be its
current module or the call module/function etc. This argument
should be optional and when omitted should default to the callee.
__FILE__ -- __traits(getFile);
__FILE_FULL_PATH__ -- __traits(getFilePath);
__MODULE__ -- __traits(getModule);
__LINE__ -- __traits(getLine);
__FUNCTION__ -- __traits(getFunction);
__PRETTY_FUNCTION__ -- __traits(getPrettyFunction);
Re: string file = __FILE__ considered harmful (and solution)
On 5/31/18 7:14 AM, bauss wrote:
Instead of these hack keywords.
Perhaps a __traits() in the compiler with the information would be
better suited like:
void foo()
{
enum caller = __traits(getCaller);
}
getCaller would return a compile-time struct with additional information
about the current module and the module/function it was called from.
How can this be possible? When inside the function, you have no idea
where you were called from.
-Steve
Re: string file = __FILE__ considered harmful (and solution)
On 5/30/2018 2:45 PM, John Colvin wrote: https://run.dlang.io/is/oMe7KQ Less elegant, but solves the problem of accidental argument adding (CallerFile acts as a barrier). Unfortunately, while it works in theory, in practice the compiler crashes LOL Please post bug reports when you find compiler crashes. Thanks!
Re: string file = __FILE__ considered harmful (and solution)
On 5/30/2018 1:27 AM, FeepingCreature wrote:
There's a very common idiom where in order to report line numbers of an error or
a log line at the callsite of a function, you pass __FILE__ and __LINE__ as
default parameters:
void foo(string file = __FILE__, size_t line = __LINE__);
What's wrong with this?
Say you add a string parameter, such as
void foo(string msg, string file = __FILE__, size_t line = __LINE__);
foo("Hello World");
Now when you accidentally grab an old version of the library, your new code will
still run, but it will believe that it's being called from file "Hello World",
line 15.
A solution:
enum E { reserved }
void foo(E e = E.reserved, string file = __FILE__, size_t line = __LINE__);
void foo(string msg, E e = E.reserved, string file = __FILE__, size_t line =
__LINE__);
Re: string file = __FILE__ considered harmful (and solution)
On Friday, 1 June 2018 at 03:14:11 UTC, Walter Bright wrote: On 5/30/2018 2:45 PM, John Colvin wrote: https://run.dlang.io/is/oMe7KQ Less elegant, but solves the problem of accidental argument adding (CallerFile acts as a barrier). Unfortunately, while it works in theory, in practice the compiler crashes LOL Please post bug reports when you find compiler crashes. Thanks! It's the same issue as this (https://issues.dlang.org/show_bug.cgi?id=18916) only for __FILE__. I already have a pending PR at https://github.com/dlang/dmd/pull/8310 which I can modify to fix for both __LINE__ and __FILE_ if I can get clarification on how it *should* work. Mike
Re: string file = __FILE__ considered harmful (and solution)
On 6/1/2018 12:30 AM, Mike Franklin wrote: I already have a pending PR at https://github.com/dlang/dmd/pull/8310 which I can modify to fix for both __LINE__ and __FILE_ if I can get clarification on how it *should* work. I followed up there. Thanks for taking care of this!
