analyzer: fix dedupe issue seen with CVE-2005-1689

analyzer: fix dedupe issue seen with CVE-2005-1689

Whilst analyzing the reproducer for detecting CVE-2005-1689
(krb5-1.4.1's src/lib/krb5/krb/recvauth.c), the analyzer reported
11 double-free diagnostics on lines of the form:

   krb5_xfree(inbuf.data);

with no deduplication occcurring.

The root cause is that the diagnostics each have a COMPONENT_REF for
the inbuf.data, but they are different trees, and the de-duplication
logic was using pointer equality.

This patch replaces the pointer equality tests with calls to a new
pending_diagnostic::same_tree_p, implemented using simple_cst_equal.

With this patch, de-duplication occurs, and only 3 diagnostics are
reported.  The 11 diagnostics are partitioned into 3 dedupe keys,
2 with 2 duplicates and 1 with 7 duplicates.

gcc/analyzer/ChangeLog:
	* diagnostic-manager.cc (saved_diagnostic::operator==): Move here
	from header.  Replace pointer equality test on m_var with call to
	pending_diagnostic::same_tree_p.
	* diagnostic-manager.h (saved_diagnostic::operator==): Move to
	diagnostic-manager.cc.
	* pending-diagnostic.cc (pending_diagnostic::same_tree_p): New.
	* pending-diagnostic.h (pending_diagnostic::same_tree_p): New.
	* sm-file.cc (file_diagnostic::subclass_equal_p): Replace pointer
	equality on m_arg with call to pending_diagnostic::same_tree_p.
	* sm-malloc.cc (malloc_diagnostic::subclass_equal_p): Likewise.
	(possible_null_arg::subclass_equal_p): Likewise.
	(null_arg::subclass_equal_p): Likewise.
	(free_of_non_heap::subclass_equal_p): Likewise.
	* sm-pattern-test.cc (pattern_match::operator==): Likewise.
	* sm-sensitive.cc (exposure_through_output_file::operator==):
	Likewise.
	* sm-taint.cc (tainted_array_index::operator==): Likewise.

gcc/testsuite/ChangeLog:
	* gcc.dg/analyzer/CVE-2005-1689-dedupe-issue.c: New test.