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From: anselm@castle.ed.ac.uk (A Lingnau)
Newsgroups: comp.lang.c
Subject: printf/scanf trouble on SPARCstation
Summary: formatted I/O crashes big program, runs OK in small program
Keywords: stdio SPARCstation big-programs
Message-ID: <5856@castle.ed.ac.uk>
Date: 22 Aug 90 08:59:28 GMT
Organization: Edinburgh University Computing Service
Lines: 25

The following problem completely beats me. I'm also rather new to
SPARCstations, and my knowledge of SPARC assembly language (ugh) is virtually
zero:

I have a large program (object size ~1/2 MB) that wants to read and write
things from/to files. However, whenever it tries to do so a segmentation fault
occurs. I have traced the error to a routine called `_doprnt()' which appears
to be a subroutine of `fprintf()'. Specifically, the error occurs at the
instruction
		_doprnt+0x24:   ld      [%o0], %o0

where, it seems, the machine wants to dereference a NULL pointer; at least
%o0 is 0 at that point.

The problem does not occur when the program in question is small (~25 KB).
Also, when I substitute `fputs()' for `fprintf()' at this point, it goes past
there O.K. but bombs when it hits a `fscanf()' later on. When I use `sprintf()'
and `fputs()' in place of `fprintf()' the thing dies, too.

The code is known to work on other UNIX machines; we're running SunOS 4.1 on
a SPARCstation 1+ and the `native' C compiler.

Any help will be greatly appreciated. Please email to anselm@castle.ed.ac.uk.

- Anselm.