Re: ld in binutils-1.9l.3

[Ian Lance Taylor <ian@cygnus.com>]

   From: hjl@nynexst.com (H.J. Lu)
   Date: Sun, 28 Aug 94 20:02:06 EDT

   > This is a weird problem that `ld' should really detect and prevent
   > (via a warning message).
   > 
   > To reproduce:
   > 
   > $ cat > test.c
   > main () { printf("this is a test\n"); }
   > ^D
   > $ gcc -o test.o test.c		(Note the missing "-c")
   > $ file test.o
   > test.o: Linux/i386 demand-paged executable (QMAGIC) not stripped
   > $ gcc -o test test.o
   > $ file test
   > test: Linux/i386 demand-paged executable (QMAGIC) not stripped
   > $ test.o
   > this is a test
   > $ test
   > [ no output ]
   > 
   > When this snuck up on us for real, it caused lots of problems and took
   > a bit of debugging to track down a bad Makefile.
   > 
   > Sometimes, they'll (twice linked binaries) run peacefully, but
   > sometimes they do bad things: seg. fault (untraceable) and suck up all
   > virtual memory are the two I've seen.
   > 
   > Could some better magic detection be put into ld?

I don't really see how to do this in a system independent fashion.  On
some systems there is no simple way to distinguish files which are
reasonable linker inputs from files which are not.

Of course, I am open to suggestions.

Note that if you define a globally visible symbol in the crt0.o file,
then you will get a multiple definition error when you attempt to link
an already linked file.  That should prevent this type of error from
occurring.

Ian