dyncall(3) BSD Library Functions Manual dyncall(3)NAMEdyncall — encapsulation of architecture-, OS- and compiler-specific func‐
tion call semantics
SYNOPSIS
#include <dyncall.h>
DCCallVM *
dcNewCallVM(DCsize size);
void
dcFree(DCCallVM * vm);
void
dcMode(DCCallVM * vm, DCint mode);
void
dcReset(DCCallVM * vm);
void
dcArgBool(DCCallVM * vm, DCbool arg);
void
dcArgChar(DCCallVM * vm, DCchar arg);
void
dcArgShort(DCCallVM * vm, DCshort arg);
void
dcArgInt(DCCallVM * vm, DCint arg);
void
dcArgLong(DCCallVM * vm, DClong arg);
void
dcArgLongLong(DCCallVM * vm, DClonglong arg);
void
dcArgFloat(DCCallVM * vm, DCfloat arg);
void
dcArgDouble(DCCallVM * vm, DCdouble arg);
void
dcArgPointer(DCCallVM * vm, DCpointer arg);
DCvoid
dcCallVoid(DCCallVM * vm, DCpointer funcptr);
DCbool
dcCallBool(DCCallVM * vm, DCpointer funcptr);
DCchar
dcCallChar(DCCallVM * vm, DCpointer funcptr);
DCshort
dcCallShort(DCCallVM * vm, DCpointer funcptr);
DCint
dcCallInt(DCCallVM * vm, DCpointer funcptr);
DClong
dcCallLong(DCCallVM * vm, DCpointer funcptr);
DClonglong
dcCallLongLong(DCCallVM * vm, DCpointer funcptr);
DCfloat
dcCallFloat(DCCallVM * vm, DCpointer funcptr);
DCdouble
dcCallDouble(DCCallVM * vm, DCpointer funcptr);
DCpointer
dcCallPointer(DCCallVM * vm, DCpointer funcptr);
void
dcArgF(DCCallVM * vm, const DCsigchar * signature, ...);
void
dcVArgF(DCCallVM * vm, const DCsigchar * signature, va_list args);
void
dcCallF(DCCallVM * vm, DCValue * result, DCpointer funcptr,
const DCsigchar * signature, ...);
void
dcVCallF(DCCallVM * vm, DCValue * result, DCpointer funcptr,
const DCsigchar * signature, va_list args);
DESCRIPTION
The dyncall library encapsulates architecture-, OS- and compiler-specific
function call semantics in a virtual "bind argument parameters from left
to right and then call" interface allowing programmers to call C func‐
tions in a completely dynamic manner.
In other words, instead of calling a function directly, the dyncall
library provides a mechanism to push the function parameters manually and
to issue the call afterwards.
Since the idea behind this concept is similar to call dispatching mecha‐
nisms of virtual machines, the object that can be dynamically loaded with
arguments, and then used to actually invoke the call, is called CallVM.
It is possible to change the calling convention used by the CallVM at
run-time. Due to the fact that nearly every platform comes with one or
more distinct calling conventions, the dyncall library project intends to
be a portable and open-source approach to the variety of compiler-spe‐
cific binary interfaces, platform specific subtleties, and so on...
dcNewCallVM() creates a new CallVM object, where size specifies the max
size of the internal stack that will be allocated and used to bind the
arguments to. Use dcFree() to destroy the CallVM object.
dcMode() sets the calling convention to use. See dyncall.h for a list of
available modes. Note that some mode/platform combinations don't make any
sense (e.g. using a PowerPC calling convention on a MIPS platform) and
are silently ignored.
dcReset() resets the internal stack of arguments and prepares it for a
new call. This function should be called after setting the call mode
(using dcMode), but prior to binding arguments to the CallVM. Use it also
when reusing a CallVM, as arguments don't get flushed automatically after
a function call invocation. Note: you should also call this function
after initial creation of the a CallVM object, as dcNewCallVM doesn't do
this, implicitly.
dcArgBool(), dcArgChar(), dcArgShort(), dcArgInt(), dcArgLong(),
dcArgLongLong(), dcArgFloat(), dcArgDouble() and dcArgPointer() are used
to bind arguments of the named types to the CallVM object. Arguments
should be bound in left to right order regarding the C function proto‐
type.
dcCallVoid(), dcCallBool(), dcCallChar(), dcCallShort(), dcCallInt(),
dcCallLong(), dcCallLongLong(), dcCallFloat(), dcCallDouble() and
dcCallPointer() call the function with the bound arguments and returning
the named type, where funcptr is a pointer to the function to call. After
the invocation of the function call, the argument values are still bound
to the CallVM and a second call using the same arguments can be issued.
Call reset() to clear the internal argument stack.
dcArgF(), dcVArgF(), dcCallF() and dcVCallF() can be used to bind argu‐
ments in a printf-style call, using a signature string encoding the argu‐
ment types and return type. The former 2 only bind the arguments to the
vm object (and ignore return types specified in the signature), whereas
the latter two issue a call to the given function pointer, afterwards.
The return value will be stored in result. For information about the
signature format, refer to the dyncall manual in PDF format.
EXAMPLE
Let's say, we want to make a call to the function:
double sqrt(double x);
Using the dyncall library, this function would be called as follows:
double r;
DCCallVM* vm = dcNewCallVM(4096);
dcMode(vm, DC_CALL_C_DEFAULT);
dcReset(vm);
dcArgDouble(vm, 4.2373);
r = dcCallDouble(vm, (DCpointer)&sqrt);
dcFree(vm);
SEE ALSOdyncallback(3), dynload(3) and the dyncall manual (available in PDF for‐
mat) for a way more detailed documentation of this library.
AUTHORS
Daniel Adler ⟨dadler@uni-goettingen.de⟩
Tassilo Philipp ⟨tphilipp@potion-studios.com⟩
BSD April 28, 2024 BSD
