1 This directory contains the libffi package, which is not part of GCC but
2 shipped with GCC as convenience.
7 libffi-3.0.8 was released on December 19, 2008. Check the libffi web
8 page for updates: <URL:http://sourceware.org/libffi/>.
14 Compilers for high level languages generate code that follow certain
15 conventions. These conventions are necessary, in part, for separate
16 compilation to work. One such convention is the "calling
17 convention". The "calling convention" is essentially a set of
18 assumptions made by the compiler about where function arguments will
19 be found on entry to a function. A "calling convention" also specifies
20 where the return value for a function is found.
22 Some programs may not know at the time of compilation what arguments
23 are to be passed to a function. For instance, an interpreter may be
24 told at run-time about the number and types of arguments used to call
25 a given function. Libffi can be used in such programs to provide a
26 bridge from the interpreter program to compiled code.
28 The libffi library provides a portable, high level programming
29 interface to various calling conventions. This allows a programmer to
30 call any function specified by a call interface description at run
33 FFI stands for Foreign Function Interface. A foreign function
34 interface is the popular name for the interface that allows code
35 written in one language to call code written in another language. The
36 libffi library really only provides the lowest, machine dependent
37 layer of a fully featured foreign function interface. A layer must
38 exist above libffi that handles type conversions for values passed
39 between the two languages.
45 Libffi has been ported to many different platforms, although this
46 release was only tested on:
51 mips o32 linux (little endian)
70 Please send additional platform test results to
71 libffi-discuss@sourceware.org.
76 [Note: before actually performing any of these installation steps,
77 you may wish to read the "Platform Specific Notes" below.]
79 First you must configure the distribution for your particular
80 system. Go to the directory you wish to build libffi in and run the
81 "configure" program found in the root directory of the libffi source
84 You may want to tell configure where to install the libffi library and
85 header files. To do that, use the --prefix configure switch. Libffi
86 will install under /usr/local by default.
88 If you want to enable extra run-time debugging checks use the the
89 --enable-debug configure switch. This is useful when your program dies
90 mysteriously while using libffi.
92 Another useful configure switch is --enable-purify-safety. Using this
93 will add some extra code which will suppress certain warnings when you
94 are using Purify with libffi. Only use this switch when using
95 Purify, as it will slow down the library.
97 Configure has many other options. Use "configure --help" to see them all.
99 Once configure has finished, type "make". Note that you must be using
100 GNU make. You can ftp GNU make from prep.ai.mit.edu:/pub/gnu.
102 To ensure that libffi is working as advertised, type "make check".
103 This will require that you have DejaGNU installed.
105 To install the library and header files, type "make install".
108 Platform Specific Notes
109 =======================
111 MIPS - Irix 5.3 & 6.x
112 ---------------------
114 Irix 6.2 and better supports three different calling conventions: o32,
115 n32 and n64. Currently, libffi only supports both o32 and n32 under
116 Irix 6.x, but only o32 under Irix 5.3. Libffi will automatically be
117 configured for whichever calling convention it was built for.
119 By default, the configure script will try to build libffi with the GNU
120 development tools. To build libffi with the SGI development tools, set
121 the environment variable CC to either "cc -32" or "cc -n32" before
122 running configure under Irix 6.x (depending on whether you want an o32
123 or n32 library), or just "cc" for Irix 5.3.
125 With the n32 calling convention, when returning structures smaller
126 than 16 bytes, be sure to provide an RVALUE that is 8 byte aligned.
127 Here's one way of forcing this:
129 double struct_storage[2];
130 my_small_struct *s = (my_small_struct *) struct_storage;
131 /* Use s for RVALUE */
133 If you don't do this you are liable to get spurious bus errors.
135 "long long" values are not supported yet.
137 You must use GNU Make to build libffi on SGI platforms.
143 There are two `System V ABI's which libffi implements for PowerPC.
144 They differ only in how small structures are returned from functions.
146 In the FFI_SYSV version, structures that are 8 bytes or smaller are
147 returned in registers. This is what GCC does when it is configured
148 for solaris, and is what the System V ABI I have (dated September
151 In the FFI_GCC_SYSV version, all structures are returned the same way:
152 by passing a pointer as the first argument to the function. This is
153 what GCC does when it is configured for linux or a generic sysv
156 EGCS 1.0.1 (and probably other versions of EGCS/GCC) also has a
157 inconsistency with the SysV ABI: When a procedure is called with many
158 floating-point arguments, some of them get put on the stack. They are
159 all supposed to be stored in double-precision format, even if they are
160 only single-precision, but EGCS stores single-precision arguments as
161 single-precision anyway. This causes one test to fail (the `many
170 (thanks to Andreas Tobler)
173 Fix for closures on sh.
174 Mark the sh/sh64 stack as non-executable.
175 (both thanks to Kaz Kojima)
179 Fix #define ARM for IcedTea users.
183 Fix x86 OpenBSD configury.
186 Enable x86 OpenBSD thanks to Thomas Heller, and
187 x86-64 FreeBSD thanks to Björn König and Andreas Tobler.
188 Clean up test instruction in README.
191 Improved x86 FreeBSD support.
192 Thanks to Björn König.
195 Fix instruction cache flushing bug on MIPS.
196 Thanks to David Daney.
199 Many changes, mostly thanks to the GCC project.
200 Cygnus Solutions is now Red Hat.
205 Raffaele Sena produces ARM port.
208 Fixed x86 long double and long long return support.
209 m68k bug fixes from Andreas Schwab.
210 Patch for DU assembler compatibility for the Alpha from Richard
214 Bug fixes and MIPS configuration changes.
217 Bug fixes and m68k port from Andreas Schwab. PowerPC port from
218 Geoffrey Keating. Various bug x86, Sparc and MIPS bug fixes.
221 Richard Henderson produces Alpha port.
224 Fixed an n32 ABI bug. New libtool, auto* support.
227 libtool is now used to generate shared and static libraries.
228 Fixed a minor portability problem reported by Russ McManus
232 Added --enable-purify-safety to keep Purify from complaining
233 about certain low level code.
234 Sparc fix for calling functions with < 6 args.
238 Added missing ffi_type_void, needed for supporting void return
239 types. Fixed test case for non MIPS machines. Cygnus Support
240 is now Cygnus Solutions.
243 Added notes about GNU make.
246 Added configuration fix for non GNU compilers.
249 Added --enable-debug configure switch. Clean-ups based on LCLint
250 feedback. ffi_mips.h is always installed. Many configuration
251 fixes. Fixed ffitest.c for sparc builds.
254 Fixed n32 problem. Many clean-ups.
257 Gordon Irlam rewrites v8.S again. Bug fixes.
260 Gordon Irlam improved the sparc port.
263 Interface changes based on feedback.
266 Sparc port complete (modulo struct passing bug).
269 Passing struct args, and returning struct values works for
270 all architectures/calling conventions. Expanded tests.
273 Added SGI n32 support. Fixed bugs in both o32 and Linux support.
277 Fixed float passing bug in mips version. Restructured some
278 of the code. Builds cleanly with SGI tools.
281 First release. No public announcement.
287 libffi was originally written by Anthony Green <green@redhat.com>.
289 The developers of the GNU Compiler Collection project have made
290 innumerable valuable contributions. See the ChangeLog file for
293 Some of the ideas behind libffi were inspired by Gianni Mariani's free
294 gencall library for Silicon Graphics machines.
296 The closure mechanism was designed and implemented by Kresten Krab
299 Major processor architecture ports were contributed by the following
302 alpha Richard Henderson
304 cris Simon Posnjak, Hans-Peter Nilsson
309 mips Anthony Green, Casey Marshall
311 pa Randolph Chung, Dave Anglin, Andreas Tobler
312 powerpc Geoffrey Keating, Andreas Tobler,
313 David Edelsohn, John Hornkvist
314 powerpc64 Jakub Jelinek
315 s390 Gerhard Tonn, Ulrich Weigand
318 sparc Anthony Green, Gordon Irlam
319 x86 Anthony Green, Jon Beniston
322 Jesper Skov and Andrew Haley both did more than their fair share of
323 stepping through the code and tracking down bugs.
325 Thanks also to Tom Tromey for bug fixes, documentation and
328 Thanks to Jim Blandy, who provided some useful feedback on the libffi
331 Andreas Tobler has done a tremendous amount of work on the testsuite.
333 Alex Oliva solved the executable page problem for SElinux.
335 The list above is almost certainly incomplete and inaccurate. I'm
336 happy to make corrections or additions upon request.
338 If you have a problem, or have found a bug, please send a note to