Created attachment 52343 [details] Reduced reproducer The attached reproducer emits two false positives from -Wanalyzer-use-of-uninitialized-value, both "when 'realloc' succeeds, moving buffer", the first of which is: <source>: In function 'main': <source>:79:34: warning: use of uninitialized value '*pollfds.fd' [CWE-457] [-Wanalyzer-use-of-uninitialized-value] 79 | pollfds[nsockets - 1].fd = accept(pollfds[0].fd, &remote, &len); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 'main': events 1-7 | | 62 | if (!pollfds) { | | ^ | | | | | (1) following 'false' branch (when 'pollfds' is non-NULL)... |...... | 67 | rc = ppoll(pollfds, nsockets, NULL, NULL); | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | | | | | (2) ...to here |...... | 74 | newpollfds = realloc(pollfds, nsockets * sizeof(*pollfds)); | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | | | | | (3) when 'realloc' succeeds, moving buffer | | (4) region created on heap here | 75 | if (!newpollfds) { | | ~ | | | | | (5) following 'false' branch (when 'newpollfds' is non-NULL)... |...... | 78 | pollfds = newpollfds; | | ~~~~~~~~~~~~~~~~~~~~ | | | | | (6) ...to here | 79 | pollfds[nsockets - 1].fd = accept(pollfds[0].fd, &remote, &len); | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | | | | | (7) use of uninitialized value '*pollfds.fd' here | On Compiler Explorer: https://godbolt.org/z/EKrnsoaY4 From downstream report: https://bugzilla.redhat.com/show_bug.cgi?id=2047926#c5
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>: https://gcc.gnu.org/g:3ef328c293a336df0aead2d72c0c5ed9781a9861 commit r12-7040-g3ef328c293a336df0aead2d72c0c5ed9781a9861 Author: David Malcolm <dmalcolm@redhat.com> Date: Wed Feb 2 16:39:12 2022 -0500 analyzer: fixes to realloc-handling [PR104369] This patch fixes various issues with how -fanalyzer handles "realloc" seen when debugging PR analyzer/104369. Previously it wasn't correctly copying over the contents of the old buffer for the success-with-move case, leading to false -Wanalyzer-use-of-uninitialized-value diagnostics. I also noticed that -fanalyzer failed to properly handle "realloc" for cases where the ptr's region had unknown dynamic extents, and an ICE for the case where a tainted value is used as a realloc size argument. This patch fixes these issues, including the false uninit diagnostics seen in PR analyzer/104369. gcc/analyzer/ChangeLog: PR analyzer/104369 * engine.cc (exploded_graph::process_node): Use the node for any diagnostics, avoiding ICE if a bifurcation update adds a saved_diagnostic, such as for a tainted realloc size. * region-model-impl-calls.cc (region_model::impl_call_realloc::success_no_move::update_model): Require the old pointer to be non-NULL to be able successfully grow in place. Use model->deref_rvalue rather than maybe_get_region to support the old pointer being symbolic. (region_model::impl_call_realloc::success_with_move::update_model): Likewise. Add a constraint that the new pointer != the old pointer. Use a sized_region when setting the value of the new region. Handle the case where we don't know the dynamic size of the old region by marking the new region as unknown. * sm-taint.cc (tainted_allocation_size::tainted_allocation_size): Update assertion to also allow for MEMSPACE_UNKNOWN. (tainted_allocation_size::emit): Likewise. (region_model::check_dynamic_size_for_taint): Likewise. gcc/testsuite/ChangeLog: PR analyzer/104369 * gcc.dg/analyzer/pr104369-1.c: New test. * gcc.dg/analyzer/pr104369-2.c: New test. * gcc.dg/analyzer/realloc-3.c: New test. * gcc.dg/analyzer/realloc-4.c: New test. * gcc.dg/analyzer/taint-realloc.c: New test. Signed-off-by: David Malcolm <dmalcolm@redhat.com>
Should be fixed by the above commit.