[petsc-dev] Need -lfl in c2html

[Satish Balay]

On Sun, 23 Feb 2014, Jed Brown wrote:

> Barry Smith <bsmith at mcs.anl.gov> writes:
> 
> > On Feb 23, 2014, at 12:47 AM, Jed Brown <jed at jedbrown.org> wrote:
> >
> >> My configure on 'master' fails with the following.  I need to link with
> >> -lfl to get the symbol yywrap.  I don't know why we haven't been
> >> encountering this before.
> >
> >    There was one user report of this a few weeks, but in all the
> >    previous years I don’t recall this ever being an issue.
> >
> >    I guess you better update maint.
> 
> Testing on petsc-mini.mcs, c2html's configure automatically finds -ll
> (/usr/lib/libl.a) and there is no -lfl.  We could check for existence of
> -lfl and pass in LEXLIB=-lfl if it works, but that could find a libfl
> floating around from a different lex implementation.  This is really
> something c2html's configure should be working out, and when I look, it
> really tries (this is why we haven't seen the issue before):

c2html's configure automatically finds -lfl on fedora and ubuntu

>>>>>>>>>>>>>>>>>>

<fedora>
$ locate libfl.
/usr/lib64/libfl.a

<ubuntu>

(next) $ locate libfl.
/usr/lib/x86_64-linux-gnu/libfl.a
/usr/lib/x86_64-linux-gnu/libfl.so

 $ nm -Ao /usr/lib/x86_64-linux-gnu/libfl.a
/usr/lib/x86_64-linux-gnu/libfl.a:libmain.o:0000000000000000 T main
/usr/lib/x86_64-linux-gnu/libfl.a:libmain.o:                 U yylex
/usr/lib/x86_64-linux-gnu/libfl.a:libyywrap.o:0000000000000000 T yywrap

$ cat /usr/lib/x86_64-linux-gnu/libfl.so
/* GNU ld script
 *                                -*- Mode: C -*-
 * libfl.so --- 
 * Author           : Manoj Srivastava ( srivasta at golden-gryphon.com ) 
 * Created On       : Mon Sep 11 13:25:55 2006
 * Created On Node  : glaurung.internal.golden-gryphon.com
 * Last Modified By : Manoj Srivastava
 * Last Modified On : Tue Sep 12 03:34:30 2006
 * Last Machine Used: glaurung.internal.golden-gryphon.com
 * Update Count     : 2
 * Status           : Unknown, Use with caution!
 * HISTORY          : 
 * Description      : 
 *
 * GNU ld script
 * When shared linking is requested, map the request to the PIC static
 * library, which is the closest we come to a shared library here.
 *
 * arch-tag: ce35efb4-3893-42c7-bdcb-56d95beba2ac
 */

INPUT( /usr/lib/x86_64-linux-gnu/libfl_pic.a )
<<<<<<<<<<<<<<<<<<<<<<<<<

So flex doesn't like .so files? Even the .so on ubuntu is a link to a static
file.

> 
> configure:1829: checking for yywrap in -lfl
> configure:1856: gcc -o conftest -g -O2   conftest.c -lfl   >&5
> /usr/lib/gcc/x86_64-unknown-linux-gnu/4.8.2/../../../../lib/libfl.so: undefined reference to `yylex'
> collect2: error: ld returned 1 exit status
> configure:1859: $? = 1
> configure: failed program was:
> #line 1837 "configure"
> #include "confdefs.h"
> 
> /* Override any gcc2 internal prototype to avoid an error.  */
> #ifdef __cplusplus
> extern "C"
> #endif
> /* We use char because int might match the return type of a gcc2
>    builtin and then its argument prototype would still apply.  */
> char yywrap ();
> int main ()
> {
>   yywrap ();
>   return 0;
> }
> configure:1876: result: no
> 
> 
> Huh, what could be happening here:
> 
> $ nm -D /usr/lib/libfl.so | grep yy
>                  U yylex
> 0000000000000740 T yywrap
> 
> 
> libfl.so defines main, which calls yylex().  We used to have a static
> library (libfl.a) in which case linking yywrap did not depend on a
> function called yylex (which is supposed to be defined outside
> libfl.so).  This causes the normal AC_CHECK_LIB(fl, yylex) to fail.

$ make
flex ./c2html.l
gcc  -O -I. -I. -DCOMPRESSION=1  -o c2html lex.yy.c ./mymain.c ./colors.c -lfl

<ok - try to get .o files for sources to do nm>
$ gcc  -O -I. -I. -DCOMPRESSION=1  -c lex.yy.c ./mymain.c ./colors.c 

$ nm -Ao c2html lex.yy.o mymain.o  colors.o |grep yylex
c2html:0000000000401393 T yylex
c2html:0000000000404603 T yylex_destroy
lex.yy.o:0000000000000463 T yylex
lex.yy.o:00000000000036d3 T yylex_destroy

Perhaps the configure test needs to define a 'yylex' symbol in the test code.

But there must be a reason why fedora/ubuntu use only .a files [and
arch switching to .so is perhaps triggering this breakage]

Satish


> Now it doesn't delight me that c2html's configure script has been edited
> From the one generated by autoconf.  I'll check with flex upstream to
> figure out what they intend to be used as a configure test now.