[Bug c++/46513] Request: Warning for use of unsafe string handling functions

[joseph at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46513

--- Comment #6 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2010-11-17 11:50:16 UTC ---
On Wed, 17 Nov 2010, noloader at gmail dot com wrote:

> I stand corrected: C1X draft dated 2010-10-04 now includes the bounds checking
> interfaces. See "C1X Draft",
> http://www.open-std.org/Jtc1/sc22/wg14/www/docs/n1516.pdf at
> http://www.open-std.org/Jtc1/sc22/wg14/www/projects.
> 
> So in addition to [nearly ubiquitous] support for strlcpy and friends, we will
> have strcpy_s and friends.

I can't imagine glibc will want to have that set of functions in libc - I 
expect it will simply omit that optional set of interfaces and not define 
__STDC_LIB_EXT1__.  Maybe someone will write a glibc add-on putting them 
in a separate library that a handful of people might then use.

*Some* of the functions there are useful, but the notion that tmpfile (for 
example) has security issues requiring tmpfile_s is nonsense.  And the 
main utility of most of those functions is to retrofit security 
improvements to old code without understanding it.  glibc has its own 
means for such retrofitting (in particular _FORTIFY_SOURCE).  In both 
cases they are really a matter of reducing the risk from certain kinds of 
bugs rather than fixing them; to fix them, you need actually to understand 
the code and determine when you should avoid arbitrary limits and allocate 
as much memory as needed (taking care about overflow when calculating 
allocation sizes) and when you should impose limits and how you should 
handle overflow of them (quietly truncating is not generally a good 
approach); safer interfaces and _FORTIFY_SOURCE should then be used *on 
top of* proper design and calculation of allocations, to reduce the risk 
of any remaining bugs, rather than as a substitute for avoiding the 
possibility of overflow or truncation in the first place.

If you wish to enforce a coding standard disallowing certain functions in 
a particular code base, you are free to use existing GCC features such as 
"#pragma GCC poison" and the "deprecated" attribute.  That seems better to 
me than GCC embedding particular assumptions about a particular set of 
functions, when everyone will have their own preferences about what 
functions should be used and whether functions are safe in a given code 
base depends on how it uses them.