[PATCH, Fortran] PR71523 - Static variables given automatic initializers with -finit-* and -fmax-stack-var-size

[Fritz Reese <fritzoreese at gmail dot com>]

RE: https://gcc.gnu.org/ml/fortran/2016-06/msg00023.html

On Thu, Jun 9, 2016 at 2:01 PM, Fritz Reese <fritzoreese@gmail.com> wrote:
> It looks like when -fautomatic and -finit-local-zero are set with
> -fmax-stack-var-size=X, an automatic initializer is generated even for
> variables larger than X which are given static storage, causing such
> static variables to have their value re-initialized upon each entry to
> their namespace.
> ...
<snip>

After doing more research I noticed PR41860
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=41860) was very similar
to this issue, so I've decided this is a bug and created PR71523
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71523). Here's a patch
for it.

The bug seems to be due to an oversight - since the size of a variable
is not known at resolution time when initializer expressions are
applied, -finit-* is too greedy in the case that the variable is large
enough to be removed from the stack according to -fmax-stack-var-size.
This patch removes automatic initializers at translation time which
were inserted by -finit-* (and inserts the appropriate static
initializer) according to -fmax-stack-var-size.

The patch passes all regression tests (on x86_64-redhat-linux),
including the two additional tests of its own demonstrating the issue.

---
Fritz Reese

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