Forcing Exception Catching At Compile Time

[Bryan Bullard]

hi,

is there a way to force the user of an object to catch exceptions of
specific type?

for instance a compile error is issued if exception 'ExeceptionXXX' thrown
by method 'ThrowsExceptio nXXX' is not caught.
thanks,
bryan

[Ron Natalie]

"Bryan Bullard" <th************ ********@sbcglo bal.net> wrote in message news:aj******** *********@newss vr23.news.prodi gy.com...

hi,

is there a way to force the user of an object to catch exceptions of
specific type?

for instance a compile error is issued if exception 'ExeceptionXXX' thrown
by method 'ThrowsExceptio nXXX' is not caught.

No way to do that. Exceptions need not be caught in the function
that throws them, or even one level up (if that were the case, they'd
have little purpose, you'd just return instead).

[Bryan Bullard]

"Ron Natalie" <ro*@sensor.com > wrote in message
news:3f******** *************** @news.newshosti ng.com...

ron-

no, not in the function that throws them. i'm not sure if my question was
clear.

i want to know if there is a way to force the compiler to check to see if an
exception is throwable by the method in question. if a call to that method
is not in a try/catch block a compile time error is produced.

similar to java.

thanks,
bryan

"Bryan Bullard" <th************ ********@sbcglo bal.net> wrote in message

news:aj******** *********@newss vr23.news.prodi gy.com...

hi,

is there a way to force the user of an object to catch exceptions of
specific type?

for instance a compile error is issued if exception 'ExeceptionXXX' thrown by method 'ThrowsExceptio nXXX' is not caught.

No way to do that. Exceptions need not be caught in the function
that throws them, or even one level up (if that were the case, they'd
have little purpose, you'd just return instead).

[Donovan Rebbechi]

In article <Zz************ *****@newssvr23 .news.prodigy.c om>, Bryan Bullard wrote:

"Ron Natalie" <ro*@sensor.com > wrote in message
news:3f******** *************** @news.newshosti ng.com...

ron-

no, not in the function that throws them. i'm not sure if my question was
clear.

i want to know if there is a way to force the compiler to check to see if an
exception is throwable by the method in question. if a call to that method
is not in a try/catch block a compile time error is produced.

similar to java.

C++ does not have checked exceptions. It has "exception specifications" , which
are not the same thing. You can google on this topic if you like. There's a
widespread feeling in the C++ community that exception specifications, as implemented
in C++, are not very helpful.

Cheers,
--
Donovan Rebbechi
http://pegasus.rutgers.edu/~elflord/

[Bryan Bullard]

"Donovan Rebbechi" <ab***@aol.co m> wrote in message
news:sl******** **********@pani x2.panix.com...

thanks for your post.

-bryan

In article <Zz************ *****@newssvr23 .news.prodigy.c om>, Bryan Bullard wrote:

"Ron Natalie" <ro*@sensor.com > wrote in message
news:3f******** *************** @news.newshosti ng.com...

ron-

no, not in the function that throws them. i'm not sure if my question was clear.

i want to know if there is a way to force the compiler to check to see if an exception is throwable by the method in question. if a call to that method is not in a try/catch block a compile time error is produced.

similar to java.

C++ does not have checked exceptions. It has "exception specifications" ,

which are not the same thing. You can google on this topic if you like. There's a widespread feeling in the C++ community that exception specifications, as implemented in C++, are not very helpful.

Cheers,
--
Donovan Rebbechi
http://pegasus.rutgers.edu/~elflord/

[Ron Natalie]

"Bryan Bullard" <th************ ********@sbcglo bal.net> wrote in message news:Zz******** *********@newss vr23.news.prodi gy.com...

"Ron Natalie" <ro*@sensor.com > wrote in message
news:3f******** *************** @news.newshosti ng.com...

ron-

no, not in the function that throws them. i'm not sure if my question was
clear.

i want to know if there is a way to force the compiler to check to see if an
exception is throwable by the method in question. if a call to that method
is not in a try/catch block a compile time error is produced.

But how is it supposed to do that? The try/catch block may be some
distance up the call stack and perhaps in a completely different translation
unit.

a.cc
int main() {
void foo();
try { foo(); } catch { exit(1); }
}

b.cc
void goo() {
throw "BLETCH";
};

void foo() {
goo();
}

So when the compiler calls b.c it's supposed to complain that foo() doesn't
catch the exepction? It is caught, but in another tu.

[Donovan Rebbechi]

In article <3f************ ***********@new s.newshosting.c om>, Ron Natalie wrote:

"Bryan Bullard" <th************ ********@sbcglo bal.net> wrote in message news:Zz******** *********@newss vr23.news.prodi gy.com...

"Ron Natalie" <ro*@sensor.com > wrote in message
news:3f******** *************** @news.newshosti ng.com...

ron-

no, not in the function that throws them. i'm not sure if my question was
clear.

i want to know if there is a way to force the compiler to check to see if an
exception is throwable by the method in question. if a call to that method
is not in a try/catch block a compile time error is produced.
But how is it supposed to do that?

The point is that you combine it with something similar to exception
specifications: you either need to specificy that the function throws
the given exception, or you need to catch it.
The try/catch block may be some
distance up the call stack and perhaps in a completely different translation
unit.
the caller of the function that issues the throw statement needs to either
catch the exception or include a specification in its declaration.

the caller of a function that includes such a specification needs to do
the same (use a try/catch or an exception specification).

The up-the-stack thing follows by induction.
a.cc
int main() {
void foo();

should be (in this way of looking at things, which doesn't work in C++):
void foo () throw (const char*);

I'm not sure why C++ doesn't have specifications implemented in this
manner.

Cheers,
--
Donovan Rebbechi
http://pegasus.rutgers.edu/~elflord/

[Bryan Bullard]

"Ron Natalie" <ro*@sensor.com > wrote in message
news:3f******** *************** @news.newshosti ng.com...

"Bryan Bullard" <th************ ********@sbcglo bal.net> wrote in message news:Zz******** *********@newss vr23.news.prodi gy.com...

"Ron Natalie" <ro*@sensor.com > wrote in message
news:3f******** *************** @news.newshosti ng.com...

ron-

no, not in the function that throws them. i'm not sure if my question was clear.

i want to know if there is a way to force the compiler to check to see if an exception is throwable by the method in question. if a call to that method is not in a try/catch block a compile time error is produced.

But how is it supposed to do that? The try/catch block may be some
distance up the call stack and perhaps in a completely different

translation unit.
which is fine if all the headers are there and there was support for it in
the language. a method would have to be declared to thrown an exception of
a certain type.

a.cc
int main() {
void foo();
try { foo(); } catch { exit(1); }
}

just as mr. rebbechi mentioned, c++ don't support exception checking.
in an exception checking scenario, the compiler would give an error if foo
is not called in a try block that catches char* or something more generic
(...) if goo or foo is declared to throw char* (or "BLETCH" as you say)

-bryan

b.cc
void goo() {
throw "BLETCH";
};

void foo() {
goo();
}

So when the compiler calls b.c it's supposed to complain that foo() doesn't catch the exepction? It is caught, but in another tu.

[Ron Natalie]

"Donovan Rebbechi" <ab***@aol.co m> wrote in message news:sl******** **********@pani x2.panix.com...

the caller of the function that issues the throw statement needs to either
catch the exception or include a specification in its declaration.
Why. By not having an exception specification, the function is free to throw
any exception.

I'm not sure why C++ doesn't have specifications implemented in this
manner.

Because the compiler is a little prejudiced against enforcing things across
translation units.

[Bryan Bullard]

"Ron Natalie" <ro*@sensor.com > wrote in message
news:3f******** *************** @news.newshosti ng.com...

"Donovan Rebbechi" <ab***@aol.co m> wrote in message news:sl******** **********@pani x2.panix.com...

the caller of the function that issues the throw statement needs to either catch the exception or include a specification in its declaration.
Why. By not having an exception specification, the function is free to

throw any exception.
can you not see the inherent problem of that? how do i know what might be
thrown?

I'm not sure why C++ doesn't have specifications implemented in this
manner.
Because the compiler is a little prejudiced against enforcing things

across translation units.
what do you call type safety?