[PATCH 2/6] detect unterminated const arrays in strlen calls (PR 86552)
The attached changes implement the detection of past-the-end reads
by strlen due to unterminated arguments.
PR tree-optimization/86552 - missing warning for reading past the end
gcc/ChangeLog:
* builtins.c (warn_string_no_nul): New function.
(expand_builtin_strlen): Warn for unterminated arrays.
(fold_builtin_strlen): Add argument. Warn for unterminated arrays.
(fold_builtin_1): Adjust call to fold_builtin_strlen.
* builtins.h (warn_string_no_nul): New function.
gcc/testsuite/ChangeLog:
* gcc.dg/warn-strlen-no-nul.c: New test.
diff --git a/gcc/builtins.c b/gcc/builtins.c
index a7aa4b2..78ced93 100644
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -150,7 +150,7 @@ static tree stabilize_va_list_loc (location_t, tree, int);
static rtx expand_builtin_expect (tree, rtx);
static tree fold_builtin_constant_p (tree);
static tree fold_builtin_classify_type (tree);
-static tree fold_builtin_strlen (location_t, tree, tree);
+static tree fold_builtin_strlen (location_t, tree, tree, tree);
static tree fold_builtin_inf (location_t, tree, int);
static tree rewrite_call_expr (location_t, tree, int, tree, int, ...);
static bool validate_arg (const_tree, enum tree_code code);
@@ -550,6 +550,36 @@ string_length (const void *ptr, unsigned eltsize, unsigned maxelts)
return n;
}
+/* For a call expression EXP to a function that expects a string argument,
+ issue a diagnostic due to it being a called with an argument NONSTR
+ that is a character array with no terminating NUL. */
+
+void
+warn_string_no_nul (location_t loc, tree exp, tree fndecl, tree nonstr)
+{
+ loc = expansion_point_location_if_in_system_header (loc);
+
+ bool warned;
+ if (exp)
+ {
+ if (!fndecl)
+ fndecl = get_callee_fndecl (exp);
+ warned = warning_at (loc, OPT_Wstringop_overflow_,
+ "%K%qD argument missing terminating nul",
+ exp, fndecl);
+ }
+ else
+ {
+ gcc_assert (fndecl);
+ warned = warning_at (loc, OPT_Wstringop_overflow_,
+ "%qD argument missing terminating nul",
+ fndecl);
+ }
+
+ if (warned && DECL_P (nonstr))
+ inform (DECL_SOURCE_LOCATION (nonstr), "referenced argument declared here");
+}
+
/* Compute the length of a null-terminated character string or wide
character string handling character sizes of 1, 2, and 4 bytes.
TREE_STRING_LENGTH is not the right way because it evaluates to
@@ -2874,7 +2904,6 @@ expand_builtin_strlen (tree exp, rtx target,
struct expand_operand ops[4];
rtx pat;
- tree len;
tree src = CALL_EXPR_ARG (exp, 0);
rtx src_reg;
rtx_insn *before_strlen;
@@ -2883,20 +2912,39 @@ expand_builtin_strlen (tree exp, rtx target,
unsigned int align;
/* If the length can be computed at compile-time, return it. */
- len = c_strlen (src, 0);
+ tree array;
+ tree len = c_strlen (src, 0, &array);
if (len)
- return expand_expr (len, target, target_mode, EXPAND_NORMAL);
+ {
+ if (array)
+ {
+ /* Array refers to the non-nul terminated constant array
+ whose length is attempted to be computed. */
+ warn_string_no_nul (EXPR_LOCATION (exp), exp, NULL_TREE, array);
+ return NULL_RTX;
+ }
+ return expand_expr (len, target, target_mode, EXPAND_NORMAL);
+ }
/* If the length can be computed at compile-time and is constant
integer, but there are side-effects in src, evaluate
src for side-effects, then return len.
E.g. x = strlen (i++ ? "xfoo" + 1 : "bar");
can be optimized into: i++; x = 3; */
- len = c_strlen (src, 1);
- if (len && TREE_CODE (len) == INTEGER_CST)
+ len = c_strlen (src, 1, &array);
+ if (len)
{
- expand_expr (src, const0_rtx, VOIDmode, EXPAND_NORMAL);
- return expand_expr (len, target, target_mode, EXPAND_NORMAL);
+ if (array)
+ {
+ warn_string_no_nul (EXPR_LOCATION (exp), exp, NULL_TREE, array);
+ return NULL_RTX;
+ }
+
+ if (TREE_CODE (len) == INTEGER_CST)
+ {
+ expand_expr (src, const0_rtx, VOIDmode, EXPAND_NORMAL);
+ return expand_expr (len, target, target_mode, EXPAND_NORMAL);
+ }
}
align = get_pointer_alignment (src) / BITS_PER_UNIT;
@@ -8339,19 +8387,30 @@ fold_builtin_classify_type (tree arg)
return build_int_cst (integer_type_node, type_to_class (TREE_TYPE (arg)));
}
-/* Fold a call to __builtin_strlen with argument ARG. */
+/* Fold a strlen call to FNDECL of TYPE, and with argument ARG. */
static tree
-fold_builtin_strlen (location_t loc, tree type, tree arg)
+fold_builtin_strlen (location_t loc, tree fndecl, tree type, tree arg)
{
if (!validate_arg (arg, POINTER_TYPE))
return NULL_TREE;
else
{
- tree len = c_strlen (arg, 0);
-
+ tree nonstr = NULL_TREE;
+ tree len = c_strlen (arg, 0, &nonstr);
if (len)
- return fold_convert_loc (loc, type, len);
+ {
+ if (loc == UNKNOWN_LOCATION && EXPR_HAS_LOCATION (arg))
+ loc = EXPR_LOCATION (arg);
+
+ /* To avoid warning multiple times about unterminated
+ arrays only warn if its length has been determined
+ and is being folded to a constant. */
+ if (nonstr)
+ warn_string_no_nul (loc, NULL_TREE, fndecl, nonstr);
+
+ return fold_convert_loc (loc, type, len);
+ }
return NULL_TREE;
}
@@ -9259,7 +9318,7 @@ fold_builtin_1 (location_t loc, tree fndecl, tree arg0)
return fold_builtin_classify_type (arg0);
case BUILT_IN_STRLEN:
- return fold_builtin_strlen (loc, type, arg0);
+ return fold_builtin_strlen (loc, fndecl, type, arg0);
CASE_FLT_FN (BUILT_IN_FABS):
CASE_FLT_FN_FLOATN_NX (BUILT_IN_FABS):
diff --git a/gcc/builtins.h b/gcc/builtins.h
index 27e6959..73b0b0b 100644
--- a/gcc/builtins.h
+++ b/gcc/builtins.h
@@ -103,7 +103,7 @@ extern bool target_char_cst_p (tree t, char *p);
extern internal_fn associated_internal_fn (tree);
extern internal_fn replacement_internal_fn (gcall *);
-
+extern void warn_string_no_nul (location_t, tree, tree, tree);
extern tree max_object_size ();
#endif /* GCC_BUILTINS_H */
diff --git a/gcc/testsuite/gcc.dg/warn-strlen-no-nul.c b/gcc/testsuite/gcc.dg/warn-strlen-no-nul.c
new file mode 100644
index 0000000..c2b0438
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/warn-strlen-no-nul.c
@@ -0,0 +1,304 @@
+/* PR tree-optimization/86552 - missing warning for reading past the end
+ of non-string arrays
+ { dg-do compile }
+ { dg-options "-O2 -Wall -ftrack-macro-expansion=0" } */
+
+extern __SIZE_TYPE__ strlen (const char*);
+
+const char a[5] = "12345"; /* { dg-message "declared here" } */
+
+int v0 = 0;
+int v1 = 1;
+
+void sink (int, ...);
+
+#define CONCAT(a, b) a ## b
+#define CAT(a, b) CONCAT(a, b)
+
+#define T(str) \
+ __attribute__ ((noipa)) \
+ void CAT (test_, __LINE__) (void) { \
+ int i0 = 0, i1 = i0 + 1, i2 = i1 + 1, i3 = i2 + 1; \
+ sink (strlen (str), i0, i1, i2, i3); \
+ } typedef void dummy_type
+
+T (a); /* { dg-warning "argument missing terminating nul" } */
+T (&a[0]); /* { dg-warning "nul" } */
+T (&a[0] + 1); /* { dg-warning "nul" } */
+T (&a[1]); /* { dg-warning "nul" } */
+T (&a[v0]); /* { dg-warning "nul" } */
+T (&a[v0] + 1); /* { dg-warning "nul" } */
+
+
+const char b[][5] = { /* { dg-message "declared here" } */
+ "12", "123", "1234", "54321"
+};
+
+T (b[0]);
+T (b[1]);
+T (b[2]);
+T (b[3]); /* { dg-warning "nul" } */
+
+T (b[i0]);
+T (b[i1]);
+T (b[i2]);
+T (b[i3]); /* { dg-warning "nul" } */
+
+T (b[v0]);
+
+T (&b[i2][i1]);
+T (&b[i2][i1] + i1);
+T (&b[i2][v0]);
+T (&b[i2][i1] + v0);
+
+T (&b[2][1]);
+T (&b[2][1] + i1);
+T (&b[2][i0]);
+T (&b[2][1] + i0);
+
+T (&b[2][1]);
+T (&b[2][1] + v0);
+T (&b[2][v0]);
+
+T (&b[3][1]); /* { dg-warning "nul" } */
+T (&b[3][1] + 1); /* { dg-warning "nul" } */
+T (&b[3][1] + i1); /* { dg-warning "nul" } */
+T (&b[3][v0]); /* { dg-warning "nul" } */
+T (&b[3][1] + v0); /* { dg-warning "nul" } */
+T (&b[3][v0] + v1); /* { dg-warning "nul" } */
+
+T (&b[i3][i1]); /* { dg-warning "nul" } */
+T (&b[i3][i1] + 1); /* { dg-warning "nul" } */
+T (&b[i3][i1] + i1); /* { dg-warning "nul" } */
+T (&b[i3][v0]); /* { dg-warning "nul" "pr86919" { xfail *-*-* } } */
+T (&b[i3][i1] + v0); /* { dg-warning "nul" "pr86919" { xfail *-*-* } } */
+T (&b[i3][v0] + v1); /* { dg-warning "nul" "pr86919" { xfail *-*-* } } */
+
+T (v0 ? "" : b[0]);
+T (v0 ? "" : b[1]);
+T (v0 ? "" : b[2]);
+T (v0 ? "" : b[3]); /* { dg-warning "nul" } */
+T (v0 ? b[0] : "");
+T (v0 ? b[1] : "");
+T (v0 ? b[2] : "");
+T (v0 ? b[3] : ""); /* { dg-warning "nul" } */
+
+T (v0 ? "" : b[i0]);
+T (v0 ? "" : b[i1]);
+T (v0 ? "" : b[i2]);
+/* The following is diagnosed but the warning location is wrong
+ (the PRE pass loses it). */
+T (v0 ? "" : b[i3]); /* { dg-warning "nul" "pr?????" { xfail *-*-* } } */
+T (v0 ? b[i0] : "");
+T (v0 ? b[i1] : "");
+T (v0 ? b[i2] : "");
+T (v0 ? b[i3] : ""); /* { dg-warning "nul" "pr?????" { xfail *-*-* } } */
+
+T (v0 ? "1234" : b[3]); /* { dg-warning "nul" } */
+T (v0 ? "1234" : b[i3]); /* { dg-warning "nul" "pr?????" { xfail *-*-* } } */
+T (v0 ? b[3] : "1234"); /* { dg-warning "nul" } */
+T (v0 ? b[i3] : "1234"); /* { dg-warning "nul" "pr?????" { xfail *-*-* } } */
+
+T (v0 ? a : b[3]); /* { dg-warning "nul" } */
+T (v0 ? b[0] : b[2]);
+T (v0 ? b[2] : b[3]); /* { dg-warning "nul" } */
+T (v0 ? b[3] : b[2]); /* { dg-warning "nul" } */
+
+T (v0 ? a : b[i3]); /* { dg-warning "nul" "pr?????" { xfail *-*-* } } */
+T (v0 ? b[i0] : b[i2]);
+T (v0 ? b[i2] : b[i3]); /* { dg-warning "nul" "pr?????" { xfail *-*-* } } */
+T (v0 ? b[i3] : b[i2]); /* { dg-warning "nul" "pr?????" { xfail *-*-* } } */
+
+T (v0 ? b[0] : &b[3][0] + 1); /* { dg-warning "nul" } */
+T (v0 ? b[0] : &b[3][0] + i1); /* { dg-warning "nul" } */
+T (v0 ? b[1] : &b[3][1] + v0); /* { dg-warning "nul" } */
+
+T (v0 ? b[i0] : &b[i3][i0] + i1); /* { dg-warning "nul" } */
+T (v0 ? b[i0] : &b[i3][i0] + i1); /* { dg-warning "nul" } */
+T (v0 ? b[i1] : &b[i3][i1] + v0); /* { dg-warning "nul" "pr?????" { xfail *-*-* } } */
+
+/* It's possible to detect the missing nul in the following two
+ expressions but GCC doesn't do it yet. */
+T (v0 ? &b[3][1] + v0 : b[2]); /* { dg-warning "nul" "bug" { xfail *-*-* } } */
+T (v0 ? &b[3][v0] : &b[3][v1]); /* { dg-warning "nul" "bug" { xfail *-*-* } } */
+
+
+struct A { char a[5], b[5]; };
+
+const struct A s = { "1234", "12345" };
+
+T (s.a);
+T (&s.a[0]);
+T (&s.a[0] + 1);
+T (&s.a[0] + v0);
+T (&s.a[1]);
+T (&s.a[1] + 1);
+T (&s.a[1] + v0);
+
+T (&s.a[i0]);
+T (&s.a[i0] + i1);
+T (&s.a[i0] + v0);
+T (&s.a[i1]);
+T (&s.a[i1] + i1);
+T (&s.a[i1] + v0);
+
+T (s.b); /* { dg-warning "nul" } */
+T (&s.b[0]); /* { dg-warning "nul" } */
+T (&s.b[0] + 1); /* { dg-warning "nul" } */
+T (&s.b[0] + v0); /* { dg-warning "nul" } */
+T (&s.b[1]); /* { dg-warning "nul" } */
+T (&s.b[1] + 1); /* { dg-warning "nul" } */
+T (&s.b[1] + i0); /* { dg-warning "nul" } */
+T (&s.b[1] + v0); /* { dg-warning "nul" } */
+
+T (&s.b[i0]); /* { dg-warning "nul" } */
+T (&s.b[i0] + i1); /* { dg-warning "nul" } */
+T (&s.b[i0] + v0); /* { dg-warning "nul" "pr86919" { xfail *-*-* } } */
+T (&s.b[i1]); /* { dg-warning "nul" } */
+T (&s.b[i1] + i1); /* { dg-warning "nul" } */
+T (&s.b[i1] + v0); /* { dg-warning "nul" "pr86919" { xfail *-*-* } } */
+
+struct B { struct A a[2]; };
+
+const struct B ba[] = {
+ { { { "123", "12345" }, { "12345", "123" } } },
+ { { { "12345", "123" }, { "123", "12345" } } },
+ { { { "1", "12" }, { "123", "1234" } } },
+ { { { "123", "1234" }, { "12345", "12" } } }
+};
+
+T (ba[0].a[0].a);
+T (&ba[0].a[0].a[0]);
+T (&ba[0].a[0].a[0] + 1);
+T (&ba[0].a[0].a[0] + v0);
+T (&ba[0].a[0].a[1]);
+T (&ba[0].a[0].a[1] + 1);
+T (&ba[0].a[0].a[1] + v0);
+
+T (ba[0].a[0].b); /* { dg-warning "nul" } */
+T (&ba[0].a[0].b[0]); /* { dg-warning "nul" } */
+T (&ba[0].a[0].b[0] + 1); /* { dg-warning "nul" } */
+T (&ba[0].a[0].b[0] + v0); /* { dg-warning "nul" } */
+T (&ba[0].a[0].b[1]); /* { dg-warning "nul" } */
+T (&ba[0].a[0].b[1] + 1); /* { dg-warning "nul" } */
+T (&ba[0].a[0].b[1] + v0); /* { dg-warning "nul" } */
+
+T (ba[0].a[1].a); /* { dg-warning "nul" } */
+T (&ba[0].a[1].a[0]); /* { dg-warning "nul" } */
+T (&ba[0].a[1].a[0] + 1); /* { dg-warning "nul" } */
+T (&ba[0].a[1].a[0] + v0); /* { dg-warning "nul" } */
+T (&ba[0].a[1].a[1]); /* { dg-warning "nul" } */
+T (&ba[0].a[1].a[1] + 1); /* { dg-warning "nul" } */
+T (&ba[0].a[1].a[1] + v0); /* { dg-warning "nul" } */
+
+T (ba[0].a[1].b);
+T (&ba[0].a[1].b[0]);
+T (&ba[0].a[1].b[0] + 1);
+T (&ba[0].a[1].b[0] + v0);
+T (&ba[0].a[1].b[1]);
+T (&ba[0].a[1].b[1] + 1);
+T (&ba[0].a[1].b[1] + v0);
+
+
+T (ba[1].a[0].a); /* { dg-warning "nul" } */
+T (&ba[1].a[0].a[0]); /* { dg-warning "nul" } */
+T (&ba[1].a[0].a[0] + 1); /* { dg-warning "nul" } */
+T (&ba[1].a[0].a[0] + v0); /* { dg-warning "nul" } */
+T (&ba[1].a[0].a[1]); /* { dg-warning "nul" } */
+T (&ba[1].a[0].a[1] + 1); /* { dg-warning "nul" } */
+T (&ba[1].a[0].a[1] + v0); /* { dg-warning "nul" } */
+
+T (ba[1].a[0].b);
+T (&ba[1].a[0].b[0]);
+T (&ba[1].a[0].b[0] + 1);
+T (&ba[1].a[0].b[0] + v0);
+T (&ba[1].a[0].b[1]);
+T (&ba[1].a[0].b[1] + 1);
+T (&ba[1].a[0].b[1] + v0);
+
+T (ba[1].a[1].a);
+T (&ba[1].a[1].a[0]);
+T (&ba[1].a[1].a[0] + 1);
+T (&ba[1].a[1].a[0] + v0);
+T (&ba[1].a[1].a[1]);
+T (&ba[1].a[1].a[1] + 1);
+T (&ba[1].a[1].a[1] + v0);
+
+T (ba[1].a[1].b); /* { dg-warning "nul" } */
+T (&ba[1].a[1].b[0]); /* { dg-warning "nul" } */
+T (&ba[1].a[1].b[0] + 1); /* { dg-warning "nul" } */
+T (&ba[1].a[1].b[0] + v0); /* { dg-warning "nul" } */
+T (&ba[1].a[1].b[1]); /* { dg-warning "nul" } */
+T (&ba[1].a[1].b[1] + 1); /* { dg-warning "nul" } */
+T (&ba[1].a[1].b[1] + v0); /* { dg-warning "nul" } */
+
+
+T (ba[2].a[0].a);
+T (&ba[2].a[0].a[0]);
+T (&ba[2].a[0].a[0] + 1);
+T (&ba[2].a[0].a[0] + v0);
+T (&ba[2].a[0].a[1]);
+T (&ba[2].a[0].a[1] + 1);
+T (&ba[2].a[0].a[1] + v0);
+
+T (ba[2].a[0].b);
+T (&ba[2].a[0].b[0]);
+T (&ba[2].a[0].b[0] + 1);
+T (&ba[2].a[0].b[0] + v0);
+T (&ba[2].a[0].b[1]);
+T (&ba[2].a[0].b[1] + 1);
+T (&ba[2].a[0].b[1] + v0);
+
+T (ba[2].a[1].a);
+T (&ba[2].a[1].a[0]);
+T (&ba[2].a[1].a[0] + 1);
+T (&ba[2].a[1].a[0] + v0);
+T (&ba[2].a[1].a[1]);
+T (&ba[2].a[1].a[1] + 1);
+T (&ba[2].a[1].a[1] + v0);
+
+
+T (ba[3].a[0].a);
+T (&ba[3].a[0].a[0]);
+T (&ba[3].a[0].a[0] + 1);
+T (&ba[3].a[0].a[0] + v0);
+T (&ba[3].a[0].a[1]);
+T (&ba[3].a[0].a[1] + 1);
+T (&ba[3].a[0].a[1] + v0);
+
+T (ba[3].a[0].b);
+T (&ba[3].a[0].b[0]);
+T (&ba[3].a[0].b[0] + 1);
+T (&ba[3].a[0].b[0] + v0);
+T (&ba[3].a[0].b[1]);
+T (&ba[3].a[0].b[1] + 1);
+T (&ba[3].a[0].b[1] + v0);
+
+T (ba[3].a[1].a); /* { dg-warning "nul" } */
+T (&ba[3].a[1].a[0]); /* { dg-warning "nul" } */
+T (&ba[3].a[1].a[0] + 1); /* { dg-warning "nul" } */
+T (&ba[3].a[1].a[0] + v0); /* { dg-warning "nul" } */
+T (&ba[3].a[1].a[1]); /* { dg-warning "nul" } */
+T (&ba[3].a[1].a[1] + 1); /* { dg-warning "nul" } */
+T (&ba[3].a[1].a[1] + v0); /* { dg-warning "nul" } */
+
+T (ba[3].a[1].b);
+T (&ba[3].a[1].b[0]);
+T (&ba[3].a[1].b[0] + 1);
+T (&ba[3].a[1].b[0] + v0);
+T (&ba[3].a[1].b[1]);
+T (&ba[3].a[1].b[1] + 1);
+T (&ba[3].a[1].b[1] + v0);
+
+
+T (v0 ? ba[0].a[0].a : ba[0].a[0].b); /* { dg-warning "nul" } */
+T (v0 ? ba[0].a[0].a : ba[0].a[0].b); /* { dg-warning "nul" } */
+
+T (v0 ? &ba[0].a[0].a[0] : &ba[3].a[1].a[0]); /* { dg-warning "nul" } */
+T (v0 ? &ba[3].a[1].a[1] : ba[0].a[0].a); /* { dg-warning "nul" } */
+
+T (v0 ? ba[0].a[0].a : ba[0].a[1].b);
+T (v0 ? ba[0].a[1].b : ba[0].a[0].a);
+
+/* Prune out warnings with no location (pr?????).
+ { dg-prune-output "cc1:" } */
