[Bug translator/23391] New: support {,foo,bar} alternation in wildcards

["fche at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=23391

            Bug ID: 23391
           Summary: support {,foo,bar} alternation in wildcards
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
          Assignee: systemtap at sourceware dot org
          Reporter: fche at redhat dot com
            Blocks: 23160
  Target Milestone: ---

The systemtap script language supports wildcards in a variety of settings:
- process probe file names
- module names
- function names
- file names
... and many others.  See calls to glob() and fnmatch() in the source tree.

In most or all of these cases, the {,a,b} csh-style alternation syntax would
come in handy.  In particular, but #23160 needs a way of intercepting
"__$arch_sys_$syscall" functions, where $arch is the alternation of "ia32" and
"x64" (on x86-64), but excludes "do" (which is an arch-sensitive lower level
handler we do NOT want to probe).

So what we'd like, in the end, is this to work:

@define arch_syscall_prefix "{ia32,x64}"  # arch-specific macro

probe kprobe.function("__" @arch_syscall_prefix "_sys_read") { .... }  #
generic

To do this, in contexts where glob(3) is used, we simply need to add the
GLOB_BRACE flag bit.  In contexts where fnmatch(3) is used, it's not so simple,
because this uses a different syntax in FNM_EXTMATCH mode.  So we need a
csh-to-ksh transformation function that takes

    fo*o{,bar,ba{do,doo}}ba[xyz]r

and maps them to

    fo*o@(|bar|ba@(do|doo))ba[xyz]r

strings, just before passing them to fnmatch(... FNM_EXTMATCH).  These can be
done probably throughout the code base, maybe subject to --compatible=4,
maybe not.


Referenced Bugs:

https://sourceware.org/bugzilla/show_bug.cgi?id=23160
[Bug 23160] 4.17 breaks syscalls tapset
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