Commit c4486e97 authored by Willy Tarreau's avatar Willy Tarreau Committed by Paul E. McKenney
Browse files

tools/nolibc: also mention how to build by just setting the include path 

Now that a few basic include files are provided, some simple portable
programs may build, which will save them from having to surround their
includes with #ifndef NOLIBC. This patch mentions how to proceed, and
enumerates the list of files that are covered.

A comprehensive list of required include files is available here:

  https://en.cppreference.com/w/c/header



Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent cec15053

tools/include/nolibc/nolibc.h

+20 −10
Original line number Diff line number Diff line
@@ -57,22 +57,32 @@ 
 * having to specify anything.

 *

 * Finally some very common libc-level functions are provided. It is the case

 * for a few functions usually found in string.h, ctype.h, or stdlib.h. Nothing

 * is currently provided regarding stdio emulation.

 * for a few functions usually found in string.h, ctype.h, or stdlib.h.

 *

 * The macro NOLIBC is always defined, so that it is possible for a program to

 * check this macro to know if it is being built against and decide to disable

 * some features or simply not to include some standard libc files.

 *

 * Ideally this file should be split in multiple files for easier long term

 * maintenance, but provided as a single file as it is now, it's quite

 * convenient to use. Maybe some variations involving a set of includes at the

 * top could work.

 * The nolibc.h file is only a convenient entry point which includes all other

 * files. It also defines the NOLIBC macro, so that it is possible for a

 * program to check this macro to know if it is being built against and decide

 * to disable some features or simply not to include some standard libc files.

 *

 * A simple static executable may be built this way :

 *      $ gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \

 *            -static -include nolibc.h -o hello hello.c -lgcc

 *

 * Simple programs meant to be reasonably portable to various libc and using

 * only a few common includes, may also be built by simply making the include

 * path point to the nolibc directory:

 *      $ gcc -fno-asynchronous-unwind-tables -fno-ident -s -Os -nostdlib \

 *            -I../nolibc -o hello hello.c -lgcc

 *

 * The available standard (but limited) include files are:

 *   ctype.h, errno.h, signal.h, stdio.h, stdlib.h, string.h, time.h

 *

 * In addition, the following ones are expected to be provided by the compiler:

 *   float.h, stdarg.h, stddef.h

 *

 * The following ones which are part to the C standard are not provided:

 *   assert.h, locale.h, math.h, setjmp.h, limits.h

 *

 * A very useful calling convention table may be found here :

 *      http://man7.org/linux/man-pages/man2/syscall.2.html

 *