Re: [PATCH -tip] perf probe: Don't compile CFI related code if elfutils is old

[Masami Hiramatsu <mhiramat@redhat.com>]

Robert Richter wrote:
> On 10.05.10 13:28:54, Arnaldo Carvalho de Melo wrote:
>> Em Mon, May 10, 2010 at 01:12:07PM -0400, Masami Hiramatsu escreveu:
>>> Check elfutils version, and if it is old don't compile
>>> CFI analysis code. This allows to compile perf with
>>> old elfutils.
>>
>> _ELFUTILS_PREREQ was introduced in:
>>
>> commit fbc7245df72ce0142f0a21fa0f4f88c97278bf60
>> Author: Roland McGrath <roland@redhat.com>
>> Date:   Tue Dec 16 17:03:03 2008 -0800
>>
>> Which was released in elfutils 0.138, guess this is coverage enough?
>> Richard, which version is in your machine?
> 
> Right, this does not work, I am using 0.131. As expected,
> "_ELFUTILS_PREREQ" is not defined:
> 
> gcc -o builtin-probe.o -c -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6 -D_FORTIFY_SOURCE=2 -Wformat -Wformat-security -Wformat-y2k -Wshadow -Winit-self -Wpacked -Wredundant-decls -Wstack-protector -Wstrict-aliasing=3 -Wswitch-default -Wswitch-enum -Wno-system-headers -Wundef -Wvolatile-register-var -Wwrite-strings -Wbad-function-cast -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wold-style-definition -Wstrict-prototypes -Wdeclaration-after-statement  -fstack-protector-all -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Iutil/include -Iarch/x86/include -I/usr/include/elfutils -DDWARF_SUPPORT -DNO_NEWT_SUPPORT -DNO_LIBPERL -DSHA1_HEADER='<openssl/sha.h>'  builtin-probe.c
> In file included from builtin-probe.c:43:
> util/probe-finder.h:47:5: error: "_ELFUTILS_PREREQ" is not defined
> util/probe-finder.h:47:21: error: missing binary operator before token "("
> make: *** [builtin-probe.o] Error 1
> 
> Why not create a compile test as for NO_DWARF in tools/perf/Makefile?

Hmm, ok, version.h is also introduced at the same time.

# git log ./config/version.h.in
commit fbc7245df72ce0142f0a21fa0f4f88c97278bf60
Author: Roland McGrath <roland@redhat.com>
Date:   Tue Dec 16 17:03:03 2008 -0800

    Install elfutils/version.h header for library compatibility checking.

So, I think we'd better set NO_DWARF if the elfutils
is older than 0.138, since we can't check API compatibility
easily.

Thank you,

-- 
Masami Hiramatsu
e-mail: mhiramat@redhat.com