re PR bootstrap/20437 (bootstrap --enable-maintainer-mode broken)

[gcc.git] / fixincludes / README

FIXINCLUDES OPERATION
=====================

See also:  http://autogen.SourceForge.net/fixinc.html

The set of fixes required was distilled down to just the data required
to specify what needed to happen for each fix.  Those data were edited
into a file named gcc/fixinc/inclhack.def.  A program called AutoGen
(http://autogen.SourceForge.net) uses these definitions to instantiate
several different templates that then produces code for a fixinclude
program (fixincl.x) and a shell script to test its functioning.  On
certain platforms (viz. those that do not have functional bidirectional
pipes), the fixincl program is split into two.  This should only concern
you on DOS and BeOS.

Regards,
	Bruce <bkorb@gnu.org>



GCC MAINTAINER INFORMATION
==========================

If you are having some problem with a system header that is either
broken by the manufacturer, or is broken by the fixinclude process,
then you will need to alter or add information to the include fix
definitions file, ``inclhack.def''.  Please also send relevant
information to gcc-bugs@gcc.gnu.org, gcc-patches@gcc.gnu.org and,
please, to me:  bkorb@gnu.org.

To make your fix, you will need to do several things:

1.  Obtain access to the AutoGen program on some platform.  It does
    not have to be your build platform, but it is more convenient.

2.  Edit "inclhack.def" to reflect the changes you need to make.
    See below for information on how to make those changes.

3.  Run the "genfixes" shell script to produce a new copy of
    the "fixincl.x" file.

4.  Rebuild the compiler and check the header causing the issue.
    Make sure it is now properly handled.  Add tests to the
    "test_text" entry(ies) that validate your fix.  This will
    help ensure that future fixes won't negate your work.

5.  Go into the fixinc build directory and type, "make check".
    You are guaranteed to have issues printed out as a result.
    Look at the diffs produced.  Make sure you have not clobbered
    the proper functioning of a different fix.  Make sure your
    fix is properly tested and it does what it is supposed to do.

6.  Now that you have the right things happening, syncronize the
    $(srcdir)/tests/base directory with the $(builddir)/tests/res
    directory.  The output of "make check" will be some diffs that
    should give you some hints about what to do.

7.  Rerun "make check" and verify that there are no issues left.


MAKING CHANGES TO INCLHACK.DEF
==============================

0.  If you are not the fixincludes maintainer, please send that
    person email about any changes you may want to make.  Thanks!

1.  Every fix must have a "hackname" that is compatible with C syntax
    for variable names and is unique without regard to alphabetic case.
    Please keep them alphabetical by this name.  :-)

2.  If the problem is known to exist only in certain files,
    then name each such file with a "files = " entry.

3.  It is relatively expensive to fire off a process to fix a source
    file, therefore write apply tests to avoid unnecessary fix
    processes.  The preferred apply tests are "select", "bypass" and
    "c_test" because they are performed internally.  "test" sends
    a command to a server shell that actually fires off one or more
    processes to do the testing.  Avoid it, if you can, but it is
    still more efficient than a fix process.  Also available is
    "mach".  If the target machine matches any of the named
    globbing-style patterns, then the machine name test will pass.
    It is desired, however, to limit the use of this test.

    These tests are required to:

    1.  Be positive for all header files that require the fix.

    It is desireable to:

    2.  Be negative as often as possible whenever the fix is not
        required, avoiding the process overhead.

    It is nice if:

    3.  The expression is as simple as possible to both
        process and understand by people.  :-)

        Please take advantage of the fact AutoGen will glue
        together string fragments.  It helps.  Also take note
        that double quote strings and single quote strings have
        different formation rules.  Double quote strings are a
        tiny superset of ANSI-C string syntax.  Single quote
        strings follow shell single quote string formation
        rules, except that the backslash is processed before
        '\\', '\'' and '#' characters (using C character syntax).

    Examples of test specifications:

      hackname = broken_assert_stdio;
      files    = assert.h;
      select   = stderr;
      bypass   = "include.*stdio.h";

    The ``broken_assert_stdio'' fix will be applied only to a file
    named "assert.h" if it contains the string "stderr" _and_ it
    does _not_ contain the expression "include.*stdio.h".

      hackname = no_double_slash;
      c_test   = "double_slash";

    The ``no_double_slash'' fix will be applied if the
    ``double_slash_test()'' function says to.  See ``fixtests.c''
    for documentation on how to include new functions into that
    module.

4.  There are currently four methods of fixing a file:

    1.  a series of sed expressions.  Each will be an individual
        "-e" argument to a single invocation of sed.

    2.  a shell script.  These scripts are _required_ to read all
        of stdin in order to avoid pipe stalls.  They may choose to
        discard the input.

    3.  Replacement text.  If the replacement is empty, then no
        fix is applied.  Otherwise, the replacement text is
        written to the output file and no further fixes are
        applied.  If you really want a no-op file, replace the
        file with a comment.

        Replacement text "fixes" must be first in this file!!

    4.  A C language subroutine method for both tests and fixes.
        See ``fixtests.c'' for instructions on writing C-language
        applicability tests and ``fixfixes.c'' for C-language fixing.
        These files also contain tables that describe the currently
        implemented fixes and tests.

    If at all possible, you should try to use one of the C language
    fixes as it is far more efficient.  There are currently five
    such fixes, three of which are very special purpose:

    i) char_macro_def - This function repairs the definition of an
        ioctl macro that presumes CPP macro substitution within
        pairs of single quote characters.

    ii) char_macro_use - This function repairs the usage of ioctl
        macros that no longer can wrap an argument with single quotes.

    iii) machine_name - This function will look at "#if", "#ifdef",
        "#ifndef" and "#elif" directive lines and replace the first
        occurrence of a non-reserved name that is traditionally
        pre-defined by the native compiler.

    The next two are for general use:

    iv) wrap - wraps the entire file with "#ifndef", "#define" and
        "#endif" self-exclusionary text.  It also, optionally, inserts
        a prolog after the "#define" and an epilog just before the
        "#endif".  You can use this for a fix as follows:

            c_fix     = wrap;
            c_fix_arg = "/* prolog text */";
            c_fix_arg = "/* epilog text */";

        If you want an epilog without a prolog, set the first "c_fix_arg"
        to the empty string.  Both or the second "c_fix_arg"s may be
        omitted and the file will still be wrapped.

	THERE IS A SPECIAL EXCEPTION TO THIS, HOWEVER:

	If the regular expression '#if.*__need' is found, then it is
	assumed that the file needs to be read and interpreted more
	than once.  However, the prolog and epilog text (if any) will
	be inserted.

    v) format - Replaces text selected with a regular expression with
        a specialized formating string.  The formatting works as follows:
        The format text is copied to the output until a '%' character
        is found.  If the character after the '%' is another '%', then
        one '%' is output and processing continues.  If the following
        character is not a digit, then the '%' and that character are
        copied and processing continues.  Finally, if the '%' *is*
        followed by a digit, that digit is used as an index into the
        regmatch_t array to replace the two characters with the matched
        text.  i.e.: "%0" is replaced by the full matching text, "%1"
        is the first matching sub-expression, etc.

        This is used as follows:

            c_fix     = format;
            c_fix_arg = "#ifndef %1\n%0\n#endif";
            c_fix_arg = "#define[ \t]+([A-Z][A-Z0-9a-z_]*).*";

        This would wrap a traditional #define inside of a "#ifndef"/"#endif"
        pair.  The second "c_fix_arg" may be omitted *IF* there is
        a select clause and the first one matches the text you want
        replaced.  You may delete text by supplying an empty string for
        the format (the first "c_fix_arg").

	Note: In general, a format c_fix may be used in place of one
	sed expression.  However, it will need to be rewritten by
	hand.  For example:

	sed = 's@^#if __GNUC__ == 2 && __GNUC_MINOR__ >= 7$'
	       '@& || __GNUC__ >= 3@';

	may be rewritten using a format c_fix as:

	c_fix     = format;
	c_fix_arg = '%0 || __GNUC__ >= 3';
	c_fix_arg = '^#if __GNUC__ == 2 && __GNUC_MINOR__ >= 7$';

	Multiple sed substitution expressions probably ought to remain sed
	expressions in order to maintain clarity.  Also note that if the
	second sed expression is the same as the first select expression,
	then you may omit the second c_fix_arg.  The select expression will
	be picked up and used in its absence.

EXAMPLES OF FIXES:
==================

      hackname = AAA_ki_iface;
      replace; /* empty replacement -> no fixing the file */

    When this ``fix'' is invoked, it will prevent any fixes
    from being applied.

    ------------------

      hackname = AAB_svr4_no_varargs;
      replace  = "/* This file was generated by fixincludes.  */\n"
                 "#ifndef _SYS_VARARGS_H\n"
                 "#define _SYS_VARARGS_H\n\n"

                 "#ifdef __STDC__\n"
                 "#include <stdarg.h>\n"
                 "#else\n"
                 "#include <varargs.h>\n"
                 "#endif\n\n"

                 "#endif  /* _SYS_VARARGS_H */\n";

    When this ``fix'' is invoked, the replacement text will be
    emitted into the replacement include file.  No further fixes
    will be applied.

    ------------------

        hackname  = hpux11_fabsf;
        files     = math.h;
        select    = "^[ \t]*#[ \t]*define[ \t]+fabsf\\(.*";
        bypass    = "__cplusplus";

        c_fix     = format;
        c_fix_arg = "#ifndef __cplusplus\n%0\n#endif";

        test_text =
        "#  define fabsf(x) ((float)fabs((double)(float)(x)))\n";

    This fix will ensure that the #define for fabs is wrapped
    with C++ protection, providing the header is not already
    C++ aware.

    ------------------

5.  Testing fixes.

    The brute force method is, of course, to configure and build
    GCC.  But you can also:

        cd ${top_builddir}/gcc
        rm -rf fixinc.sh include/ stmp-fixinc
        make stmp-fixinc

    I would really recommend, however:

        cd ${top_builddir}/gcc/fixinc
        make check

    To do this, you *must* have autogen installed on your system.
    The "check" step will proceed to construct a shell script that
    will exercise all the fixes, using the sample test_text
    provided with each fix.  Once done, the changes made will
    be compared against the changes saved in the source directory.
    If you are changing the tests or fixes, the change will likely
    be highlighted.