dyncall(3)

NAME
dyncall - encapsulation of architecture-, OS- and compiler-specific function 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 functions 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 mechanisms 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-specific 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 prototype.

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 arguments in a printf-style call, using a signature string encoding the argument 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);

CONFORMING TO
The dyncall library needs at least a c99 compiler with additional support for anonymous structs/unions (which were introduced officially in c11). Given that those are generally supported by pretty much all major c99 conforming compilers (as default extension), it should build fine with a c99 toolchain. Strictly speaking, dyncall conforms to c11, though.

SEE ALSO
dyncallback(3), dynload(3) and the dyncall manual (available in HTML and PDF format) for more information.

AUTHORS
Daniel Adler <dadler@uni-goettingen.de> Tassilo Philipp <tphilipp@potion-studios.com>