stdlib: Re-implement free (environ) compatibility kludge for setenv

For the originally failing application (userhelper from usermode),
it is not actually necessary to call realloc on the environ
pointer.  Yes, there will be a memory leak because the application
assigns a heap-allocated pointer to environ that it never frees,
but this leak was always there: the old realloc-based setenv had
a hidden internal variable, last_environ, that was used in a similar
way to __environ_array_list.  The application is not impacted by
the leak anyway because the relevant operations do not happen in
a loop.

The change here just uses a separte heap allocation and points
environ to that.  This means that if an application calls
free (environ) and restores the environ pointer to the value
at process start, and does not modify the environment further,
nothing bad happens.

This change should not invalidate any previous testing that went into
the original getenv thread safety change, commit 7a61e7f557a97ab597d6
("stdlib: Make getenv thread-safe in more cases").

The new test cases are modeled in part on the env -i use case from
bug 32588 (with !DO_MALLOC && !DO_EARLY_SETENV), and the previous
stdlib/tst-setenv-malloc test.  The DO_MALLOC && !DO_EARLY_SETENV
case in the new test should approximate what userhelper from the
usermode package does.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

0 files changed, 0 insertions, 0 deletions