I have a variable like this:
int *p;
Sometimes this points to an int location containing the address of a
void(void) function.
How can I cast it so that I can call that function?
I've tried casting to void **(void). The compiler keeps saying such a cast
is illegal.
(It should compile to something like this in x86 code:
mov esi,[p]
call [esi]
)
Thanks,
-- Bartc 3 2090
"Bartc" <bc@freeuk.comw rote in message
news:nh******** **********@text .news.virginmed ia.com...
>I have a variable like this:
int *p;
Sometimes this points to an int location containing the address of a
void(void) function.
How can I cast it so that I can call that function?
I've tried casting to void **(void). The compiler keeps saying such a cast
is illegal.
(It should compile to something like this in x86 code:
mov esi,[p]
call [esi]
)
According to the C99 standard, it may be possible as a common extension:
"J.5.7 Function pointer casts
1 A pointer to an object or to void may be cast to a pointer to a function,
allowing data to
be invoked as a function (6.5.4).
2 A pointer to a function may be cast to a pointer to an object or to void,
allowing a function to be inspected or modified (for example, by a debugger)
(6.5.4)."
Show the actual code you are trying to use.
** Posted from http://www.teranews.com **
Bartc wrote:
I have a variable like this:
int *p;
Sometimes this points to an int location containing the address of a
void(void) function.
How can I cast it so that I can call that function?
I've tried casting to void **(void). The compiler keeps saying such a cast
is illegal.
(It should compile to something like this in x86 code:
mov esi,[p]
call [esi]
)
The call would look like
((void(*)(void) )*p)();
.... which might be more readable with a typedef (I dislike
typedefs that name object pointer types, but for function
pointers they are often helpful):
typedef void (*VoidOfVoid)(v oid);
((VoidOfVoid)*p )();
Be aware that treating an int value as a function pointer
is not something the Standard says must work. It is quite
likely to fail spectacularly in a 64-bit setting ...
-- Er*********@sun .com
"Eric Sosman" <Er*********@su n.comwrote in message
news:1208464501 .259090@news1nw k...
Bartc wrote:
>I have a variable like this:
int *p;
Sometimes this points to an int location containing the address of a void(void) function.
How can I cast it so that I can call that function?
I've tried casting to void **(void). The compiler keeps saying such a cast is illegal.
The call would look like
((void(*)(void) )*p)();
... which might be more readable with a typedef (I dislike
typedefs that name object pointer types, but for function
pointers they are often helpful):
That works perfectly, thanks!
I don't care what it looks like, it's only used in one place; in context it
looks like this (part of byte-code opcode dispatcher):
stopped=0;
do {
((void(*)(void) )*pcptr)();
} while (!stopped);
-- Bartc This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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