Re: PATCH: Avoid accidentally opening files for write

Mark Mitchell
2005-06-07T15:53:28Z

Nick Clifton wrote:
> Hi Mark,
>
>> Tested on x86_64-unknown-linux-gnu. OK to apply?
>
>
> Have you tested this patch in both POSIX and non-POSIX build
> environments ?

I did not test in a non-POSIX *build* environment, but I did test in a
non-POIX *target* environment. In particular, I built a MinGW GDB using
a GNU/Linux host, and verified that this fixed the bug. (I used an
older version of GDB that still had a tendency to mangle its output;
using this patch stopped it from doing the mangling because it no longer
tried to write out the file.)

> assume so, but it would be nice to have that confirmed. Also with a
> patch to a generic part of BFD it would be good if you could also test
> with a --enable-targets=all build, just to make sure.

I didn't know about that, but will try it before check-in. Just a
build, or should I try to run some kind of testsuite as well? (Is there
a way to run the binutils testuite on all targets all at once?)

>> ! if (strchr (mode, '+'))
>> ! nbfd->direction = both_direction;
>> ! else if (strchr (mode, 'r'))
>> ! nbfd->direction = read_direction;
>> ! else
>> ! nbfd->direction = write_direction;
>
>
> This assumes that the contents of 'mode' are well defined. Is this the
> case for non-POSIX environments ? For example can we be sure that the
> character 'R' is never used to indicate read-only status, or that an OS
> might allow a file created with just "a" to have the newly-written-to
> parts read back, effectively making "a" a read-and-write mode ? What I
> am getting at is, should bfd_fopen() take an explicit extra parameter
> which tells BFD whether this file is intended for reading, writing or
> both ?

Hmm. In practice, we always use one of the FOPEN_* macros as an
argument, and these do follow the rules implied by what I wrote. But, I
could tighten the test to check for just what ISO C requires, which is
that the characters must occur at the start of the string, so using
strchr is probably incorrect. OK to make that change before check-in,
or would you like me to resubmit?

I'm not aware of OSes that do as you say, but, in any case, I don't
think we need to worry about OSes that accept other variations. Clients
of BFD should be using the standard syntax. It's OK if they use OS
extensions, but I think it's reasonable to say that if they mean "read"
they use "r" and not "R".

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
(916) 791-8304