As an example I sent a bug-report on 26 Nov to tell that the fix included
below is necessary to compile pg95-current on Ultrix with Digital's
standard C compiler c89. In fact I think that this fix is needed
for any C compiler sticking very close the standard, see my discussion
in the original bug report.

Erik Bertelsen

From: Massimo Dal Zotto <dz@cs.unitn.it>

Submitted by: Massimo Dal Zotto <dz@cs.unitn.it>

Submitted by: Massimo Dal Zotto <dz@cs.unitn.it>

Submitted by: Massimo Dal Zotto <dz@cs.unitn.it>

Excuse me.

                                      ^ - deleted
                free(settings->opt.fieldSep);

cc1: warnings being treated as errors
datum.c: In function `DatumGetSize':
datum.c:57: warning: unsigned value >= 0 is always 1
gmake[3]: *** [datum.o] Error 1

There was:
    if (byVal) {
        if (len >= 0 && len <= sizeof(Datum)) {

but len has type Size (unsigned int) and so now there is:
    if (byVal) {
        if (len <= sizeof(Datum)) {

cc1: warnings being treated as errors
exc.c: In function 'ExcRaise':
exc.c:186: warning: passing arg 1 of 'Longjmp' from incompatible pointer type
gmake[3]: *** [exc.o] Error 1

Now we have:
#if defined (JMP_BUF)
        longjmp(efp->context, 1);
#else
        siglongjmp(efp->context, 1);
#endif

cc1: warnings being treated as errors
transsup.c: In function `TransBlockGetLastTransactionIdStatus':
transsup.c:122: warning: unsigned value >= 0 is always 1
gmake[3]: *** [transsup.o] Error 1
...

is eliminated (now I can copy 2000000-table from file without memmory
exhausting).

Plus: sigjmp_buf/jmp_buf is backwards, so backend doesn't compile.