analyzer: fix false positives from -Wanalyzer-infinite-recursion [PR108524]

analyzer: fix false positives from -Wanalyzer-infinite-recursion [PR108524]

Reject -Wanalyzer-infinite-recursion diagnostics in which control flow
has been affected by conjured_svalues between the initial call to a
function and the subsequent entry to that function.  This prevents false
positives such as in qemu's recursive JSON parser where function calls are
changing state in the rest of the program (e.g. consuming tokens), despite
the modelled state being effectively identical at both nested entrypoints.

gcc/analyzer/ChangeLog:
	PR analyzer/108524
	* analyzer.h (class feasible_node): New forward decl.
	* diagnostic-manager.cc (epath_finder::get_best_epath): Add "pd"
	param.
	(epath_finder::explore_feasible_paths): Likewise.
	(epath_finder::process_worklist_item): Likewise.  Use it to call
	pending_diagnostic::check_valid_fpath_p on the final fpath to
	give pending_diagnostic a way to add additional restrictions on
	feasibility.
	(saved_diagnostic::calc_best_epath): Pass pending_diagnostic to
	epath_finder::get_best_epath.
	* infinite-recursion.cc: Include "analyzer/feasible-graph.h".
	(infinite_recursion_diagnostic::check_valid_fpath_p): New.
	(infinite_recursion_diagnostic::fedge_uses_conjured_svalue_p): New.
	(infinite_recursion_diagnostic::expr_uses_conjured_svalue_p): New.
	* pending-diagnostic.h (pending_diagnostic::check_valid_fpath_p):
	New vfunc.

gcc/testsuite/ChangeLog:
	PR analyzer/108524
	* gcc.dg/analyzer/infinite-recursion-pr108524-1.c: New test.
	* gcc.dg/analyzer/infinite-recursion-pr108524-2.c: New test.
	* gcc.dg/analyzer/infinite-recursion-pr108524-qobject-json-parser.c:
	New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>