Hi, David,
Thank you for fixing this issue!
> On Feb 2, 2022, at 9:06 AM, David Malcolm via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>
> GCC 12 has gained two features for dealing with uninitialized variables:
>
> (a) a new -Wanalyzer-use-of-uninitialized-value warning within -fanalyzer
> for interprocedural path-sensitive detection of ununit uses, and
>
> (b) a new -ftrivial-auto-var-init option for mitigating some uses of
> uninit variables
>
> It turns out that using (b) was thwarting (a), as it led to -fanalyzer
> seeing calls to IFN_DEFERRED_INIT, which -fanalyzer wasn't
> special-casing, thus treating it as initializing the variables in
> question, and thus silencing -Wanalyzer-use-of-uninitialized-value on
> them.
>
> invoke.texi says:
>
> "GCC still considers an automatic variable that doesn't have an explicit
> initializer as uninitialized, @option{-Wuninitialized} will still report
> warning messages on such automatic variables."
>
> and thus -Wanalyzer-use-of-uninitialized-value ought to as well.
Then should we updated the invoke.texi to include this as well?
thanks.
Qing
>
> This patch adds special-case handling to -fanalyzer for
> IFN_DEFERRED_INIT, so that -fanalyzer will warn on uninit uses of
> variables that are mitigated by -ftrivial-auto-var-init.
>
> Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.
>
> Not strictly a regression, but as this affects two new GCC 12 features
> it seems appropriate to fix in stage 4.
>
> Pushed to trunk as r12-6997-g9b4eee5fd158c4ee75d1f1000debbf5082fb9b56.
>
> gcc/analyzer/ChangeLog:
> PR analyzer/104270
> * region-model.cc (region_model::on_call_pre): Handle
> IFN_DEFERRED_INIT.
>
> gcc/testsuite/ChangeLog:
> PR analyzer/104270
> * gcc.dg/analyzer/uninit-trivial-auto-var-init-pattern.c: New
> test.
> * gcc.dg/analyzer/uninit-trivial-auto-var-init-uninitialized.c:
> New test.
> * gcc.dg/analyzer/uninit-trivial-auto-var-init-zero.c: New test.
>
> Signed-off-by: David Malcolm <dmalc...@redhat.com>
> ---
> gcc/analyzer/region-model.cc | 10 ++++++++++
> .../analyzer/uninit-trivial-auto-var-init-pattern.c | 7 +++++++
> .../uninit-trivial-auto-var-init-uninitialized.c | 7 +++++++
> .../analyzer/uninit-trivial-auto-var-init-zero.c | 7 +++++++
> 4 files changed, 31 insertions(+)
> create mode 100644
> gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-pattern.c
> create mode 100644
> gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-uninitialized.c
> create mode 100644
> gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-zero.c
>
> diff --git a/gcc/analyzer/region-model.cc b/gcc/analyzer/region-model.cc
> index 6810cf508d9..4c312b053f8 100644
> --- a/gcc/analyzer/region-model.cc
> +++ b/gcc/analyzer/region-model.cc
> @@ -1109,6 +1109,16 @@ region_model::on_call_pre (const gcall *call,
> region_model_context *ctxt,
>
> bool unknown_side_effects = false;
>
> + /* Special-case for IFN_DEFERRED_INIT.
> + We want to report uninitialized variables with -fanalyzer (treating
> + -ftrivial-auto-var-init= as purely a mitigation feature).
> + Handle IFN_DEFERRED_INIT by treating it as no-op: don't touch the
> + lhs of the call, so that it is still uninitialized from the point of
> + view of the analyzer. */
> + if (gimple_call_internal_p (call)
> + && gimple_call_internal_fn (call) == IFN_DEFERRED_INIT)
> + return false;
> +
> /* Some of the cases below update the lhs of the call based on the
> return value, but not all. Provide a default value, which may
> get overwritten below. */
> diff --git
> a/gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-pattern.c
> b/gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-pattern.c
> new file mode 100644
> index 00000000000..0b78dc65267
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-pattern.c
> @@ -0,0 +1,7 @@
> +/* { dg-additional-options "-ftrivial-auto-var-init=pattern" } */
> +
> +int test_1 (void)
> +{
> + int i; /* { dg-message "region created on stack here" } */
> + return i; /* { dg-warning "use of uninitialized value 'i'" } */
> +}
> diff --git
> a/gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-uninitialized.c
> b/gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-uninitialized.c
> new file mode 100644
> index 00000000000..124d3a327b8
> --- /dev/null
> +++
> b/gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-uninitialized.c
> @@ -0,0 +1,7 @@
> +/* { dg-additional-options "-ftrivial-auto-var-init=uninitialized" } */
> +
> +int test_1 (void)
> +{
> + int i; /* { dg-message "region created on stack here" } */
> + return i; /* { dg-warning "use of uninitialized value 'i'" } */
> +}
> diff --git
> a/gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-zero.c
> b/gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-zero.c
> new file mode 100644
> index 00000000000..ef7dc674867
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/analyzer/uninit-trivial-auto-var-init-zero.c
> @@ -0,0 +1,7 @@
> +/* { dg-additional-options "-ftrivial-auto-var-init=zero" } */
> +
> +int test_1 (void)
> +{
> + int i; /* { dg-message "region created on stack here" } */
> + return i; /* { dg-warning "use of uninitialized value 'i'" } */
> +}
> --
> 2.26.3
>
