it seems, that since my debian unstable upgraded from  flex 2.5.4a-14 to 2.5.4a-15, I can't compile the Zend Engine anymore. It throws an error in zend_ini_parser.c and if I compare a zend_ini_parser.c genearated with the -14 version and one from -15 version, there are indeed differences where the error occurs. 

here's the error-mesage from make:

/bin/sh ../libtool --mode=compile gcc -DHAVE_CONFIG_H -I. -I. -I../main   -DLINUX=22 -DUSE_HSREGEX -I../TSRM  -g  -Wall -prefer-pic -c zend_ini_scanner.c
gcc -DHAVE_CONFIG_H -I. -I. -I../main -DLINUX=22 -DUSE_HSREGEX -I../TSRM -g -Wall -c zend_ini_scanner.c     -fPIC -DPIC -o zend_ini_scanner.lo
zend_ini_scanner.c: In function `ini_lex':
zend_ini_scanner.c:826: warning: label `find_rule' defined but not used
zend_ini_scanner.c: In function `yy_get_next_buffer':
zend_ini_scanner.c:1243: `errno' undeclared (first use in this function)
zend_ini_scanner.c:1243: (Each undeclared identifier is reported only once
zend_ini_scanner.c:1243: for each function it appears in.)
zend_ini_scanner.c:1243: `EINTR' undeclared (first use in this function)
./zend_ini_scanner.l: At top level:
zend_ini_scanner.c:1900: warning: `yy_flex_realloc' defined but not used
zend_ini_scanner.c:1350: warning: `yyunput' defined but not used
make[1]: *** [zend_ini_scanner.lo] Error 1
make[1]: Leaving directory `/opt/cvs/php4/Zend'
make: *** [all-recursive] Error 1

and here the diff between the both zend_ini_scanner.c versions:

--- Z/zend_ini_scanner.c        Thu Jan 10 01:28:37 2002
+++ Zend/zend_ini_scanner.c     Thu Jan 10 01:52:57 2002
@@ -698,9 +698,17 @@
                        YY_FATAL_ERROR( "input in flex scanner failed" ); \
                result = n; \
                } \
-       else if ( ((result = fread( buf, 1, max_size, yyin )) == 0) \
-                 && ferror( yyin ) ) \
-               YY_FATAL_ERROR( "input in flex scanner failed" );
+       errno=0; \
+       while ( (result = fread(buf, 1, max_size, yyin))==0 && ferror(yyin)) \
+       { \
+               if( errno != EINTR) \
+               { \
+                       YY_FATAL_ERROR( "input in flex scanner failed" ); \
+                       break; \
+               } \
+               errno=0; \
+               clearerr(yyin); \
+       }
 #endif

and here the relevant part from the debian-changelog:


flex (2.5.4a-15) unstable; urgency=low

  * if a signal is delivered while the parser is in the read routine
    (coded by flex), the result is flex reports and YY_FATAL_ERROR causing
    plan to exit.  The race condition appears much more frequently than
    one might expect because plan spends a good deal of time in read
    routine while gcc is preparing the input. I cleaned up another problem
    case beyond what is given in the patch.                  closes: Bug#125611


I have no idea about this flex stuff, so maybe someone else out there can fix that :)