On 15 Jun 2009, at 07:45, leledumbo wrote:
Suppose I have a program written in C:
#include <stdio.h>
int main() {
return 1 / 0;
}
and a Pascal program that calls it:
program prog;
{$mode objfpc}{$H+}
uses
SysUtils;
begin
try
ExecuteProcess('tes.exe','');
except
on e: Exception do begin
WriteLn(e.Message);
end;
end;
WriteLn('Done').
end.
How can I catch the exception generated by the C program
You cannot. Exceptions are program-local events. They do not propagate
outside the process they are raised in (regardless of whether they are
transformed into language-level exception objects or not).
(note that it can be a DLL too)?
Executed via ExecuteProcess? If you mean calling a function in a dll,
then it depends at least on the following:
1) if the dll function catches the exception itself, you won't see it
(although if it's an FPC-compiled dll, then the exception will
currently always propagate to the main program under Windows: http://bugs.freepascal.org/view.php?id=12974)
, even if it reraises it afterwards (because then it will have been
transformed from an OS-level exception into a language-level
exception, and
a) FPC's exception model is different from that of all other
compilers, and
b) even if the dll is compiled with FPC and if you would be able to
catch the exception in the dll, FPC's implementation currently does
not allow propagating language-level exceptions across dll/program
(nor dll/dll) boundaries
b) if the dll function does not catch the exception
2) if the dll/dll function does not catch the system-level exception,
you should be able to catch it in the FPC function that called that
function.
The above approach doesn't catch it. The C program terminates
abnormally as
usual, and the Pascal program goes by itself (proven by string
'Done' gets
written correctly).
Most program exit with a non-zero exit code if some error occurred.
You have to use that, or some other form of explicit communication
(e.g., have the child process write something to a file, use some form
of shared memory in the parent and the child, ...).
Jonas
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