Re: RFA: don't read coff line number unless we have symbols too

[Jim Blandy <jimb at redhat dot com>]

"Paul N. Hilfinger" <hilfingr@otisco.mckusick.com> writes:
> Jim Blandy wrote :
> > 
> > Ping to the COFF maintainer: this patch needs review.
> > 
> > Jim Blandy <jimb@redhat.com> writes:
> > 
> > > 2002-03-06  Jim Blandy  <jimb@redhat.com>
> > > 
> > >     * coffread.c (coff_symfile_read): Don't try to read the line
> > >     number table from disk if the image file doesn't have a symbol
> > >     table; we'll never actually look at the info anyway, and Windows
> > >     ships DLL's with bogus file offsets for the line number data.
> 
> But apparently, on Interix, you can get files with valid line numbers and 
> no symbols when all the .o's come from VC and are linked by ld.  So the 
> line-number info is perhaps not entirely useless.  Is this change a 
> space-saving move, or a fix for a more serious problem?

See the comment from the patch:

!   /* Only read line number information if we have symbols.
! 
!      On Windows NT, some of the system's DLL's have sections with
!      PointerToLinenumbers fields that are non-zero, but point at
!      random places within the image file.  (In the case I found,
!      KERNEL32.DLL's .text section has a line number info pointer that
!      points into the middle of the string `lib\\i386\kernel32.dll'.)
! 
!      However, these DLL's also have no symbols.  The line number
!      tables are meaningless without symbols.  And in fact, GDB never
!      uses the line number information unless there are symbols.  So we
!      can avoid spurious error messages (and maybe run a little
!      faster!) by not even reading the line number table unless we have
!      symbols.  */