c, analyzer: fix ICE with -fanalyzer and -Wunused-macros [PR107711]

PR analyzer/107711 reports an ICE since r13-4073-gd8aba860b34203 with
the combination of -fanalyzer and -Wunused-macros.

The issue is that in c_translation_unit::consider_macro's call to
cpp_create_reader I was passing "ident_hash" for use by the the new
reader, but that takes ownership of that hash_table, so that ident_hash
erroneously gets freed when c_translation_unit::consider_macro calls
cpp_destroy, leading to a use-after-free in -Wunused-macros, where:

(gdb) p pfile->hash_table->pfile == pfile
$23 = false

and it's instead pointing at the freed reader from consider_macro,
leading to a use-after-free ICE.

Fixed thusly.

gcc/c/ChangeLog:
	PR analyzer/107711
	* c-parser.cc (ana::c_translation_unit::consider_macro): Pass NULL
	to cpp_create_reader, rather than ident_hash, so that the new
	reader gets its own hash table.

gcc/testsuite/ChangeLog:
	PR analyzer/107711
	* gcc.dg/analyzer/named-constants-Wunused-macros.c: New test.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
index f3c7999..1bbb39f 100644
--- a/gcc/c/c-parser.cc
+++ b/gcc/c/c-parser.cc
@@ -1717,7 +1717,7 @@ private:
       return NULL_TREE;
 
     cpp_reader *old_parse_in = parse_in;
-    parse_in = cpp_create_reader (CLK_GNUC89, ident_hash, line_table);
+    parse_in = cpp_create_reader (CLK_GNUC89, NULL, line_table);
 
     pretty_printer pp;
     pp_string (&pp, (const char *) tok.val.str.text);