Here are the left over patches I used to build GDB on DJGPP.

GDB changes:

- "missing sentinel in function calls" warnings:

  NULL is not a pointer in djgpp, it's #define NULL 0.  Recent gcc's
  bark on cases like the concat calls I'm fixing, if the last argument
  is not a pointer.

- cp-name-parse.y

  There's a call to snprintf in it.  DJGPP gets it from libiberty.

  I needed to include config.h, so HAVE_DECL_SNPRINTF is defined when
  libiberty.h is included, which then declares snprintf.

- gdb_select.h

  Include sys/types.h to pick up fd_set.

  Include <time.h> in posix-hdep.c, because that's where select is
  declared.  (?)

The readline bits, the patch explains what's needed.

Here's the error log
gcc -DHAVE_CONFIG_H    -I. -I../../readline -DRL_LIBRARY_VERSION='"5.1"' -O0 -g3
 -c ../../readline/support/wcwidth.c
In file included from ../../readline/support/wcwidth.c:9:
c:/djgpp/include/wchar.h:24: error: expected '=', ',', ';', 'asm' 
or '__attribut
e__' before 'typedef'
../../readline/support/wcwidth.c: In function 'wcwidth':
../../readline/support/wcwidth.c:130: warning: comparison is always false due 
to
 limited range of data type
../../readline/support/wcwidth.c:130: warning: comparison is always true due 
to
limited range of data type
make.exe: *** [wcwidth.o] Error 1

- libbfd 

 cc1.exe: warnings being treated as errors
 ../../bfd/archive.c: In function '_bfd_archive_bsd_update_armap_timestamp':
 ../../bfd/archive.c:2314: warning: comparison between signed and unsigned

 time_t in djgpp is unsigned int, armap_timestamp is long.
 There's a comment at the definition of armap_timestamp, claiming that it
 isn't time_t until more compilers support it.

-- 
Pedro Alves