question about env and function malloc

[Rich Felker]

On Thu, Dec 18, 2014 at 03:44:10AM -0200, Alexandre Oliva wrote:
> [Cc:ing the list]
> 
> On Dec 17, 2014, MaShimiao <mashimiao.fnst@cn.fujitsu.com> wrote:
> 
> > But, the description of env in glibc manual says if a function accesses 
> > environment with getenv() of similar, without any guard, then it should be
> > marked with env. it doesn't mention any special functions.
> > Do you think we should add some words to remind users that there are some special
> > conditions in which even a function calls getenv(), it will not be marked with env.
> > Just like malloc() or free().
> > Or we just add explanations in the description of each special functions?
> 
> I think a note at the exception point should be enough, as in the patch
> below.

This is a conformance issue; for the purpose of safety with respect to
modifying the environment in a multi-threaded program, the set of
standard functions allowed to access the environment is fixed by POSIX
and does not include malloc. The only conforming way functions outside
this fixed set can use the environment is to probe it during program
initialization (before any application-level code runs) and save the
result.

Rich