cmd/asm: fix crash triggered by nested #define
A panic was in place for an impossible condition that turned
out to be possible if one used a macro to define a macro.
Another go-fuzz "win".
Fixes #12654.
Change-Id: I0a7bb0f0eabb260c986bf7a2288860c78d8db1af
Reviewed-on: https://go-review.googlesource.com/14777
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/src/cmd/asm/internal/lex/lex_test.go b/src/cmd/asm/internal/lex/lex_test.go
index 14ffffe..f606ffe 100644
--- a/src/cmd/asm/internal/lex/lex_test.go
+++ b/src/cmd/asm/internal/lex/lex_test.go
@@ -226,6 +226,35 @@
),
"C.\n",
},
+ {
+ "nested #define",
+ lines(
+ "#define A #define B THIS",
+ "A",
+ "B",
+ ),
+ "THIS.\n",
+ },
+ {
+ "nested #define with args",
+ lines(
+ "#define A #define B(x) x",
+ "A",
+ "B(THIS)",
+ ),
+ "THIS.\n",
+ },
+ /* This one fails. See comment in Slice.Col.
+ {
+ "nested #define with args",
+ lines(
+ "#define A #define B (x) x",
+ "A",
+ "B(THIS)",
+ ),
+ "x.\n",
+ },
+ */
}
func TestLex(t *testing.T) {
diff --git a/src/cmd/asm/internal/lex/slice.go b/src/cmd/asm/internal/lex/slice.go
index e94106b..b0d5429 100644
--- a/src/cmd/asm/internal/lex/slice.go
+++ b/src/cmd/asm/internal/lex/slice.go
@@ -44,8 +44,16 @@
}
func (s *Slice) Col() int {
- // Col is only called when defining a macro, which can't reach here.
- panic("cannot happen: slice col")
+ // TODO: Col is only called when defining a macro and all it cares about is increasing
+ // position to discover whether there is a blank before the parenthesis.
+ // We only get here if defining a macro inside a macro.
+ // This imperfect implementation means we cannot tell the difference between
+ // #define A #define B(x) x
+ // and
+ // #define A #define B (x) x
+ // The first has definition of B has an argument, the second doesn't. Because we let
+ // text/scanner strip the blanks for us, this is extremely rare, hard to fix, and not worth it.
+ return s.pos
}
func (s *Slice) SetPos(line int, file string) {
