opts: SANITIZE_ADDRESS wrongly cleared [PR108543]

Here we crash on a null fndecl ultimately because we haven't defined
the built-ins described in sanitizer.def.  So
builtin_decl_explicit (BUILT_IN_ASAN_POINTER_SUBTRACT);
returns NULL_TREE, causing an ICE later.

DEF_SANITIZER_BUILTIN only actually defines the built-ins when flag_sanitize
has SANITIZE_ADDRESS, or some of the other SANITIZE_*, but it doesn't check
SANITIZE_KERNEL_ADDRESS or SANITIZE_USER_ADDRESS.  Unfortunately, with
-fsanitize=address -fno-sanitize=kernel-address
or
-fsanitize=kernel-address -fno-sanitize=address
SANITIZE_ADDRESS ends up being unset from flag_sanitize even though
_USER/_KERNEL are set.  That's because -fsanitize=address means
SANITIZE_ADDRESS | SANITIZE_USER_ADDRESS and -fsanitize=kernel-address
is SANITIZE_ADDRESS | SANITIZE_KERNEL_ADDRESS but parse_sanitizer_options
does
  flags &= ~sanitizer_opts[i].flag;
so the subsequent -fno- unsets SANITIZE_ADDRESS.  Then no sanitizer
built-ins are actually defined.

I'm not sure why SANITIZE_ADDRESS isn't just SANITIZE_USER_ADDRESS |
SANITIZE_KERNEL_ADDRESS, I don't think we need 3 bits.

	PR middle-end/108543

gcc/ChangeLog:

	* opts.cc (parse_sanitizer_options): Don't always clear SANITIZE_ADDRESS
	if it was previously set.

gcc/testsuite/ChangeLog:

	* c-c++-common/asan/pointer-subtract-5.c: New test.
	* c-c++-common/asan/pointer-subtract-6.c: New test.
	* c-c++-common/asan/pointer-subtract-7.c: New test.
	* c-c++-common/asan/pointer-subtract-8.c: New test.

5 files changed, 68 insertions, 1 deletions

diff --git a/gcc/opts.cc b/gcc/opts.cc
index 9ba47d7..a032cd4 100644
--- a/gcc/opts.cc
+++ b/gcc/opts.cc
@@ -2246,7 +2246,14 @@ parse_sanitizer_options (const char *p, location_t loc, int scode,
 		  flags |= sanitizer_opts[i].flag;
 	      }
 	    else
-	      flags &= ~sanitizer_opts[i].flag;
+	      {
+		flags &= ~sanitizer_opts[i].flag;
+		/* Don't always clear SANITIZE_ADDRESS if it was previously
+		   set: -fsanitize=address -fno-sanitize=kernel-address should
+		   leave SANITIZE_ADDRESS set.  */
+		if (flags & (SANITIZE_KERNEL_ADDRESS | SANITIZE_USER_ADDRESS))
+		  flags |= SANITIZE_ADDRESS;
+	      }
 	    found = true;
 	    break;
 	  }
diff --git a/gcc/testsuite/c-c++-common/asan/pointer-subtract-5.c b/gcc/testsuite/c-c++-common/asan/pointer-subtract-5.c
new file mode 100644
index 0000000..867eda0
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/asan/pointer-subtract-5.c
@@ -0,0 +1,15 @@
+/* PR middle-end/108543 */
+/* { dg-do compile  } */
+/* { dg-options "-fsanitize=address -fno-sanitize=kernel-address -fsanitize=pointer-subtract" } */
+
+struct S {
+  long _M_p;
+};
+
+typedef struct S S;
+
+__PTRDIFF_TYPE__
+f (S __x, S __y)
+{
+  return &__x._M_p - &__y._M_p;
+}
diff --git a/gcc/testsuite/c-c++-common/asan/pointer-subtract-6.c b/gcc/testsuite/c-c++-common/asan/pointer-subtract-6.c
new file mode 100644
index 0000000..785b90b
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/asan/pointer-subtract-6.c
@@ -0,0 +1,15 @@
+/* PR middle-end/108543 */
+/* { dg-do compile  } */
+/* { dg-options "-fsanitize=kernel-address -fno-sanitize=address -fsanitize=pointer-subtract" } */
+
+struct S {
+  long _M_p;
+};
+
+typedef struct S S;
+
+__PTRDIFF_TYPE__
+f (S __x, S __y)
+{
+  return &__x._M_p - &__y._M_p;
+}
diff --git a/gcc/testsuite/c-c++-common/asan/pointer-subtract-7.c b/gcc/testsuite/c-c++-common/asan/pointer-subtract-7.c
new file mode 100644
index 0000000..11b6340
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/asan/pointer-subtract-7.c
@@ -0,0 +1,15 @@
+/* PR middle-end/108543 */
+/* { dg-do compile  } */
+/* { dg-options "-fno-sanitize=kernel-address -fsanitize=address -fsanitize=pointer-subtract" } */
+
+struct S {
+  long _M_p;
+};
+
+typedef struct S S;
+
+__PTRDIFF_TYPE__
+f (S __x, S __y)
+{
+  return &__x._M_p - &__y._M_p;
+}
diff --git a/gcc/testsuite/c-c++-common/asan/pointer-subtract-8.c b/gcc/testsuite/c-c++-common/asan/pointer-subtract-8.c
new file mode 100644
index 0000000..ac2b9c3
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/asan/pointer-subtract-8.c
@@ -0,0 +1,15 @@
+/* PR middle-end/108543 */
+/* { dg-do compile  } */
+/* { dg-options "-fno-sanitize=address -fsanitize=kernel-address -fsanitize=pointer-subtract" } */
+
+struct S {
+  long _M_p;
+};
+
+typedef struct S S;
+
+__PTRDIFF_TYPE__
+f (S __x, S __y)
+{
+  return &__x._M_p - &__y._M_p;
+}