/Modules/_ctypes/libffi_osx/README
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1This directory contains the libffi package, which is not part of GCC but 2shipped with GCC as convenience. 3 4Status 5====== 6 7libffi-2.00 has not been released yet! This is a development snapshot! 8 9libffi-1.20 was released on October 5, 1998. Check the libffi web 10page for updates: <URL:http://sources.redhat.com/libffi/>. 11 12 13What is libffi? 14=============== 15 16Compilers for high level languages generate code that follow certain 17conventions. These conventions are necessary, in part, for separate 18compilation to work. One such convention is the "calling 19convention". The "calling convention" is essentially a set of 20assumptions made by the compiler about where function arguments will 21be found on entry to a function. A "calling convention" also specifies 22where the return value for a function is found. 23 24Some programs may not know at the time of compilation what arguments 25are to be passed to a function. For instance, an interpreter may be 26told at run-time about the number and types of arguments used to call 27a given function. Libffi can be used in such programs to provide a 28bridge from the interpreter program to compiled code. 29 30The libffi library provides a portable, high level programming 31interface to various calling conventions. This allows a programmer to 32call any function specified by a call interface description at run 33time. 34 35Ffi stands for Foreign Function Interface. A foreign function 36interface is the popular name for the interface that allows code 37written in one language to call code written in another language. The 38libffi library really only provides the lowest, machine dependent 39layer of a fully featured foreign function interface. A layer must 40exist above libffi that handles type conversions for values passed 41between the two languages. 42 43 44Supported Platforms and Prerequisites 45===================================== 46 47Libffi has been ported to: 48 49 SunOS 4.1.3 & Solaris 2.x (SPARC-V8, SPARC-V9) 50 51 Irix 5.3 & 6.2 (System V/o32 & n32) 52 53 Intel x86 - Linux (System V ABI) 54 55 Alpha - Linux and OSF/1 56 57 m68k - Linux (System V ABI) 58 59 PowerPC - Linux (System V ABI, Darwin, AIX) 60 61 ARM - Linux (System V ABI) 62 63Libffi has been tested with the egcs 1.0.2 gcc compiler. Chances are 64that other versions will work. Libffi has also been built and tested 65with the SGI compiler tools. 66 67On PowerPC, the tests failed (see the note below). 68 69You must use GNU make to build libffi. SGI's make will not work. 70Sun's probably won't either. 71 72If you port libffi to another platform, please let me know! I assume 73that some will be easy (x86 NetBSD), and others will be more difficult 74(HP). 75 76 77Installing libffi 78================= 79 80[Note: before actually performing any of these installation steps, 81 you may wish to read the "Platform Specific Notes" below.] 82 83First you must configure the distribution for your particular 84system. Go to the directory you wish to build libffi in and run the 85"configure" program found in the root directory of the libffi source 86distribution. 87 88You may want to tell configure where to install the libffi library and 89header files. To do that, use the --prefix configure switch. Libffi 90will install under /usr/local by default. 91 92If you want to enable extra run-time debugging checks use the the 93--enable-debug configure switch. This is useful when your program dies 94mysteriously while using libffi. 95 96Another useful configure switch is --enable-purify-safety. Using this 97will add some extra code which will suppress certain warnings when you 98are using Purify with libffi. Only use this switch when using 99Purify, as it will slow down the library. 100 101Configure has many other options. Use "configure --help" to see them all. 102 103Once configure has finished, type "make". Note that you must be using 104GNU make. SGI's make will not work. Sun's probably won't either. 105You can ftp GNU make from prep.ai.mit.edu:/pub/gnu. 106 107To ensure that libffi is working as advertised, type "make test". 108 109To install the library and header files, type "make install". 110 111 112Using libffi 113============ 114 115 The Basics 116 ---------- 117 118Libffi assumes that you have a pointer to the function you wish to 119call and that you know the number and types of arguments to pass it, 120as well as the return type of the function. 121 122The first thing you must do is create an ffi_cif object that matches 123the signature of the function you wish to call. The cif in ffi_cif 124stands for Call InterFace. To prepare a call interface object, use the 125following function: 126 127ffi_status ffi_prep_cif(ffi_cif *cif, ffi_abi abi, 128 unsigned int nargs, 129 ffi_type *rtype, ffi_type **atypes); 130 131 CIF is a pointer to the call interface object you wish 132 to initialize. 133 134 ABI is an enum that specifies the calling convention 135 to use for the call. FFI_DEFAULT_ABI defaults 136 to the system's native calling convention. Other 137 ABI's may be used with care. They are system 138 specific. 139 140 NARGS is the number of arguments this function accepts. 141 libffi does not yet support vararg functions. 142 143 RTYPE is a pointer to an ffi_type structure that represents 144 the return type of the function. Ffi_type objects 145 describe the types of values. libffi provides 146 ffi_type objects for many of the native C types: 147 signed int, unsigned int, signed char, unsigned char, 148 etc. There is also a pointer ffi_type object and 149 a void ffi_type. Use &ffi_type_void for functions that 150 don't return values. 151 152 ATYPES is a vector of ffi_type pointers. ARGS must be NARGS long. 153 If NARGS is 0, this is ignored. 154 155 156ffi_prep_cif will return a status code that you are responsible 157for checking. It will be one of the following: 158 159 FFI_OK - All is good. 160 161 FFI_BAD_TYPEDEF - One of the ffi_type objects that ffi_prep_cif 162 came across is bad. 163 164 165Before making the call, the VALUES vector should be initialized 166with pointers to the appropriate argument values. 167 168To call the the function using the initialized ffi_cif, use the 169ffi_call function: 170 171void ffi_call(ffi_cif *cif, void *fn, void *rvalue, void **avalues); 172 173 CIF is a pointer to the ffi_cif initialized specifically 174 for this function. 175 176 FN is a pointer to the function you want to call. 177 178 RVALUE is a pointer to a chunk of memory that is to hold the 179 result of the function call. Currently, it must be 180 at least one word in size (except for the n32 version 181 under Irix 6.x, which must be a pointer to an 8 byte 182 aligned value (a long long). It must also be at least 183 word aligned (depending on the return type, and the 184 system's alignment requirements). If RTYPE is 185 &ffi_type_void, this is ignored. If RVALUE is NULL, 186 the return value is discarded. 187 188 AVALUES is a vector of void* that point to the memory locations 189 holding the argument values for a call. 190 If NARGS is 0, this is ignored. 191 192 193If you are expecting a return value from FN it will have been stored 194at RVALUE. 195 196 197 198 An Example 199 ---------- 200 201Here is a trivial example that calls puts() a few times. 202 203 #include <stdio.h> 204 #include <ffi.h> 205 206 int main() 207 { 208 ffi_cif cif; 209 ffi_type *args[1]; 210 void *values[1]; 211 char *s; 212 int rc; 213 214 /* Initialize the argument info vectors */ 215 args[0] = &ffi_type_uint; 216 values[0] = &s; 217 218 /* Initialize the cif */ 219 if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, 1, 220 &ffi_type_uint, args) == FFI_OK) 221 { 222 s = "Hello World!"; 223 ffi_call(&cif, puts, &rc, values); 224 /* rc now holds the result of the call to puts */ 225 226 /* values holds a pointer to the function's arg, so to 227 call puts() again all we need to do is change the 228 value of s */ 229 s = "This is cool!"; 230 ffi_call(&cif, puts, &rc, values); 231 } 232 233 return 0; 234 } 235 236 237 238 Aggregate Types 239 --------------- 240 241Although libffi has no special support for unions or bit-fields, it is 242perfectly happy passing structures back and forth. You must first 243describe the structure to libffi by creating a new ffi_type object 244for it. Here is the definition of ffi_type: 245 246 typedef struct _ffi_type 247 { 248 unsigned size; 249 short alignment; 250 short type; 251 struct _ffi_type **elements; 252 } ffi_type; 253 254All structures must have type set to FFI_TYPE_STRUCT. You may set 255size and alignment to 0. These will be calculated and reset to the 256appropriate values by ffi_prep_cif(). 257 258elements is a NULL terminated array of pointers to ffi_type objects 259that describe the type of the structure elements. These may, in turn, 260be structure elements. 261 262The following example initializes a ffi_type object representing the 263tm struct from Linux's time.h: 264 265 struct tm { 266 int tm_sec; 267 int tm_min; 268 int tm_hour; 269 int tm_mday; 270 int tm_mon; 271 int tm_year; 272 int tm_wday; 273 int tm_yday; 274 int tm_isdst; 275 /* Those are for future use. */ 276 long int __tm_gmtoff__; 277 __const char *__tm_zone__; 278 }; 279 280 { 281 ffi_type tm_type; 282 ffi_type *tm_type_elements[12]; 283 int i; 284 285 tm_type.size = tm_type.alignment = 0; 286 tm_type.elements = &tm_type_elements; 287 288 for (i = 0; i < 9; i++) 289 tm_type_elements[i] = &ffi_type_sint; 290 291 tm_type_elements[9] = &ffi_type_slong; 292 tm_type_elements[10] = &ffi_type_pointer; 293 tm_type_elements[11] = NULL; 294 295 /* tm_type can now be used to represent tm argument types and 296 return types for ffi_prep_cif() */ 297 } 298 299 300 301Platform Specific Notes 302======================= 303 304 Intel x86 305 --------- 306 307There are no known problems with the x86 port. 308 309 Sun SPARC - SunOS 4.1.3 & Solaris 2.x 310 ------------------------------------- 311 312You must use GNU Make to build libffi on Sun platforms. 313 314 MIPS - Irix 5.3 & 6.x 315 --------------------- 316 317Irix 6.2 and better supports three different calling conventions: o32, 318n32 and n64. Currently, libffi only supports both o32 and n32 under 319Irix 6.x, but only o32 under Irix 5.3. Libffi will automatically be 320configured for whichever calling convention it was built for. 321 322By default, the configure script will try to build libffi with the GNU 323development tools. To build libffi with the SGI development tools, set 324the environment variable CC to either "cc -32" or "cc -n32" before 325running configure under Irix 6.x (depending on whether you want an o32 326or n32 library), or just "cc" for Irix 5.3. 327 328With the n32 calling convention, when returning structures smaller 329than 16 bytes, be sure to provide an RVALUE that is 8 byte aligned. 330Here's one way of forcing this: 331 332 double struct_storage[2]; 333 my_small_struct *s = (my_small_struct *) struct_storage; 334 /* Use s for RVALUE */ 335 336If you don't do this you are liable to get spurious bus errors. 337 338"long long" values are not supported yet. 339 340You must use GNU Make to build libffi on SGI platforms. 341 342 ARM - System V ABI 343 ------------------ 344 345The ARM port was performed on a NetWinder running ARM Linux ELF 346(2.0.31) and gcc 2.8.1. 347 348 349 350 PowerPC System V ABI 351 -------------------- 352 353There are two `System V ABI's which libffi implements for PowerPC. 354They differ only in how small structures are returned from functions. 355 356In the FFI_SYSV version, structures that are 8 bytes or smaller are 357returned in registers. This is what GCC does when it is configured 358for solaris, and is what the System V ABI I have (dated September 3591995) says. 360 361In the FFI_GCC_SYSV version, all structures are returned the same way: 362by passing a pointer as the first argument to the function. This is 363what GCC does when it is configured for linux or a generic sysv 364target. 365 366EGCS 1.0.1 (and probably other versions of EGCS/GCC) also has a 367inconsistency with the SysV ABI: When a procedure is called with many 368floating-point arguments, some of them get put on the stack. They are 369all supposed to be stored in double-precision format, even if they are 370only single-precision, but EGCS stores single-precision arguments as 371single-precision anyway. This causes one test to fail (the `many 372arguments' test). 373 374 375What's With The Crazy Comments? 376=============================== 377 378You might notice a number of cryptic comments in the code, delimited 379by /*@ and @*/. These are annotations read by the program LCLint, a 380tool for statically checking C programs. You can read all about it at 381<http://larch-www.lcs.mit.edu:8001/larch/lclint/index.html>. 382 383 384History 385======= 386 3871.20 Oct-5-98 388 Raffaele Sena produces ARM port. 389 3901.19 Oct-5-98 391 Fixed x86 long double and long long return support. 392 m68k bug fixes from Andreas Schwab. 393 Patch for DU assembler compatibility for the Alpha from Richard 394 Henderson. 395 3961.18 Apr-17-98 397 Bug fixes and MIPS configuration changes. 398 3991.17 Feb-24-98 400 Bug fixes and m68k port from Andreas Schwab. PowerPC port from 401 Geoffrey Keating. Various bug x86, Sparc and MIPS bug fixes. 402 4031.16 Feb-11-98 404 Richard Henderson produces Alpha port. 405 4061.15 Dec-4-97 407 Fixed an n32 ABI bug. New libtool, auto* support. 408 4091.14 May-13-97 410 libtool is now used to generate shared and static libraries. 411 Fixed a minor portability problem reported by Russ McManus 412 <mcmanr@eq.gs.com>. 413 4141.13 Dec-2-96 415 Added --enable-purify-safety to keep Purify from complaining 416 about certain low level code. 417 Sparc fix for calling functions with < 6 args. 418 Linux x86 a.out fix. 419 4201.12 Nov-22-96 421 Added missing ffi_type_void, needed for supporting void return 422 types. Fixed test case for non MIPS machines. Cygnus Support 423 is now Cygnus Solutions. 424 4251.11 Oct-30-96 426 Added notes about GNU make. 427 4281.10 Oct-29-96 429 Added configuration fix for non GNU compilers. 430 4311.09 Oct-29-96 432 Added --enable-debug configure switch. Clean-ups based on LCLint 433 feedback. ffi_mips.h is always installed. Many configuration 434 fixes. Fixed ffitest.c for sparc builds. 435 4361.08 Oct-15-96 437 Fixed n32 problem. Many clean-ups. 438 4391.07 Oct-14-96 440 Gordon Irlam rewrites v8.S again. Bug fixes. 441 4421.06 Oct-14-96 443 Gordon Irlam improved the sparc port. 444 4451.05 Oct-14-96 446 Interface changes based on feedback. 447 4481.04 Oct-11-96 449 Sparc port complete (modulo struct passing bug). 450 4511.03 Oct-10-96 452 Passing struct args, and returning struct values works for 453 all architectures/calling conventions. Expanded tests. 454 4551.02 Oct-9-96 456 Added SGI n32 support. Fixed bugs in both o32 and Linux support. 457 Added "make test". 458 4591.01 Oct-8-96 460 Fixed float passing bug in mips version. Restructured some 461 of the code. Builds cleanly with SGI tools. 462 4631.00 Oct-7-96 464 First release. No public announcement. 465 466 467Authors & Credits 468================= 469 470libffi was written by Anthony Green <green@cygnus.com>. 471 472Portions of libffi were derived from Gianni Mariani's free gencall 473library for Silicon Graphics machines. 474 475The closure mechanism was designed and implemented by Kresten Krab 476Thorup. 477 478The Sparc port was derived from code contributed by the fine folks at 479Visible Decisions Inc <http://www.vdi.com>. Further enhancements were 480made by Gordon Irlam at Cygnus Solutions <http://www.cygnus.com>. 481 482The Alpha port was written by Richard Henderson at Cygnus Solutions. 483 484Andreas Schwab ported libffi to m68k Linux and provided a number of 485bug fixes. 486 487Geoffrey Keating ported libffi to the PowerPC. 488 489Raffaele Sena ported libffi to the ARM. 490 491Jesper Skov and Andrew Haley both did more than their fair share of 492stepping through the code and tracking down bugs. 493 494Thanks also to Tom Tromey for bug fixes and configuration help. 495 496Thanks to Jim Blandy, who provided some useful feedback on the libffi 497interface. 498 499If you have a problem, or have found a bug, please send a note to 500green@cygnus.com.