analyzer: fix taint false +ve due to overzealous state purging [PR112977]
gcc/analyzer/ChangeLog:
PR analyzer/112977
* engine.cc (impl_region_model_context::on_liveness_change): Pass
m_ext_state to sm_state_map::on_liveness_change.
* program-state.cc (sm_state_map::on_svalue_leak): Guard removal
of map entry based on can_purge_p.
(sm_state_map::on_liveness_change): Add ext_state param. Add
workaround for bad interaction between state purging and
alt-inherited sm-state.
* program-state.h (sm_state_map::on_liveness_change): Add
ext_state param.
* sm-taint.cc
(taint_state_machine::has_alt_get_inherited_state_p): New.
(taint_state_machine::can_purge_p): Return false for "has_lb" and
"has_ub".
* sm.h (state_machine::has_alt_get_inherited_state_p): New vfunc.
gcc/testsuite/ChangeLog:
PR analyzer/112977
* gcc.dg/plugin/plugin.exp: Add taint-pr112977.c.
* gcc.dg/plugin/taint-pr112977.c: New test.
Signed-off-by: David Malcolm <dmalcolm@redhat.com>