Can't finish compilation on Slackware

[VOC-LINK]

Hello,
I already found some help in the thread "Problems compiling/linking on opensuse #6" - but still there are errors preventing me from finishing compilation. I execute "./configure" using following line:
./configure CFLAGS='-std=gnu90' --enable-tkconfig=/usr/lib --enable-tclconfig=/usr/lib

It seems to fix many-many "first declared here"-kind type of errors, but still compilation gets interrupted and I got messages like these:

Loading ./gcl_cmpinit.lsp
Finished loading ./gcl_cmpinit.lsp
End of Pass 1.
End of Pass 2.
In file included from gcl_sharp.c:2:0:
/home/me/.Eterm/gcl/unixport/../h/cmpinclude.h:32:6: error: "<" is not a valid filename

34 3 4

  ^

/home/me/.Eterm/gcl/unixport/../h/cmpinclude.h:33:20: error: expected identifier or '(' before 'void'
((void *)0)
^
/home/me/.Eterm/gcl/unixport/../h/cmpinclude.h:33:27: error: expected ')' before numeric constant
((void *)0)
^
/home/me/.Eterm/gcl/unixport/../h/cmpinclude.h:35:6: error: "<" is not a valid filename

35

  ^

/home/me/.Eterm/gcl/unixport/../h/cmpinclude.h:42:6: error: "<" is not a valid filename

40 3 4

So I took a peek into the file cmpinclude.h and its contents looks like this (lines 31-35):

#define OBJNULL

34 3 4

             ((void *)0)

35

Replacing -std=gnu90 parameter with -std=gnu89 means no change. I'm using Slackware64 14.2 with gcc 5.5.0. TCL/Tk 8.4.20.

Perhaps somebody could point out, what more should I change/add to finish compilation?

[VOC-LINK]

OK, found the solution here: https://lists.gnu.org/archive/html/gcl-devel/2015-06/msg00001.html
"This fixes the problem:
sed -i 's,$(CC) -E,& -P,' makefile"