Am Dienstag, dem 31.10.2023 um 22:19 +0000 schrieb Joseph Myers:
> On Tue, 31 Oct 2023, Martin Uecker wrote:
>
> > > + if (TREE_CODE (arg) == INTEGER_CST
> > > + && tree_int_cst_lt (arg, TYPE_SIZE_UNIT (ttl)))
>
> What if TYPE_SIZE_UNIT (ttl) is not an INTEGER_CST? I don't see any tests
> of the case of assigning to a pointer to a variably sized type.
>
Right. Thanks! Revised version attached.
Martin
c: Add Walloc-size to warn about insufficient size in allocations [PR71219]
Add option Walloc-size that warns about allocations that have
insufficient storage for the target type of the pointer the
storage is assigned to. Added to Wextra.
PR c/71219
gcc:
* doc/invoke.texi: Document -Walloc-size option.
gcc/c-family:
* c.opt (Walloc-size): New option.
gcc/c:
* c-typeck.cc (convert_for_assignment): Add warning.
gcc/testsuite:
* gcc.dg/Walloc-size-1.c: New test.
* gcc.dg/Walloc-size-2.c: New test.
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 44b9c862c14..29d3d789a49 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -331,6 +331,10 @@ Walloca
C ObjC C++ ObjC++ Var(warn_alloca) Warning
Warn on any use of alloca.
+Walloc-size
+C ObjC Var(warn_alloc_size) Warning LangEnabledBy(C ObjC, Wextra)
+Warn when allocating insufficient storage for the target type of the assigned
pointer.
+
Walloc-size-larger-than=
C ObjC C++ LTO ObjC++ Var(warn_alloc_size_limit) Joined Host_Wide_Int ByteSize
Warning Init(HOST_WIDE_INT_MAX)
-Walloc-size-larger-than=<bytes> Warn for calls to allocation functions
that
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 0de4662bfc6..16fadfb5468 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -7347,6 +7347,34 @@ convert_for_assignment (location_t location, location_t
expr_loc, tree type,
"request for implicit conversion "
"from %qT to %qT not permitted in C++", rhstype, type);
+ /* Warn of new allocations that are not big enough for the target
+ type. */
+ tree fndecl;
+ if (warn_alloc_size
+ && TREE_CODE (rhs) == CALL_EXPR
+ && (fndecl = get_callee_fndecl (rhs)) != NULL_TREE
+ && DECL_IS_MALLOC (fndecl))
+ {
+ tree fntype = TREE_TYPE (fndecl);
+ tree fntypeattrs = TYPE_ATTRIBUTES (fntype);
+ tree alloc_size = lookup_attribute ("alloc_size", fntypeattrs);
+ if (alloc_size)
+ {
+ tree args = TREE_VALUE (alloc_size);
+ int idx = TREE_INT_CST_LOW (TREE_VALUE (args)) - 1;
+ /* For calloc only use the second argument. */
+ if (TREE_CHAIN (args))
+ idx = TREE_INT_CST_LOW (TREE_VALUE (TREE_CHAIN (args))) - 1;
+ tree arg = CALL_EXPR_ARG (rhs, idx);
+ if (TREE_CODE (arg) == INTEGER_CST
+ && INTEGER_CST == TREE_CODE (TYPE_SIZE_UNIT (ttl))
+ && tree_int_cst_lt (arg, TYPE_SIZE_UNIT (ttl)))
+ warning_at (location, OPT_Walloc_size, "allocation of "
+ "insufficient size %qE for type %qT with "
+ "size %qE", arg, ttl, TYPE_SIZE_UNIT (ttl));
+ }
+ }
+
/* See if the pointers point to incompatible address spaces. */
asl = TYPE_ADDR_SPACE (ttl);
asr = TYPE_ADDR_SPACE (ttr);
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 5a9284d635c..815a33d4b87 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -8138,6 +8138,16 @@ always leads to a call to another @code{cold} function
such as wrappers of
C++ @code{throw} or fatal error reporting functions leading to @code{abort}.
@end table
+@opindex Wno-alloc-size
+@opindex Walloc-size
+@item -Walloc-size
+Warn about calls to allocation functions decorated with attribute
+@code{alloc_size} that specify insufficient size for the target type of
+the pointer the result is assigned to, including those to the built-in
+forms of the functions @code{aligned_alloc}, @code{alloca},
+@code{calloc},
+@code{malloc}, and @code{realloc}.
+
@opindex Wno-alloc-zero
@opindex Walloc-zero
@item -Walloc-zero
diff --git a/gcc/testsuite/gcc.dg/Walloc-size-1.c
b/gcc/testsuite/gcc.dg/Walloc-size-1.c
new file mode 100644
index 00000000000..61806f58192
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Walloc-size-1.c
@@ -0,0 +1,36 @@
+/* Tests the warnings for insufficient allocation size.
+ { dg-do compile }
+ { dg-options "-Walloc-size" }
+ * */
+#include <stdlib.h>
+#include <alloca.h>
+
+struct b { int x[10]; };
+
+void fo0(void)
+{
+ struct b *p = malloc(sizeof *p);
+}
+
+void fo1(void)
+{
+ struct b *p = malloc(sizeof p); /* { dg-warning
"allocation of insufficient size" } */
+}
+
+void fo2(void)
+{
+ struct b *p = alloca(sizeof p); /* { dg-warning
"allocation of insufficient size" } */
+}
+
+void fo3(void)
+{
+ struct b *p = calloc(1, sizeof p); /* { dg-warning "allocation of
insufficient size" } */
+}
+
+void g(struct b* p);
+
+void fo4(void)
+{
+ g(malloc(4)); /* { dg-warning "allocation of
insufficient size" } */
+}
+
diff --git a/gcc/testsuite/gcc.dg/Walloc-size-2.c
b/gcc/testsuite/gcc.dg/Walloc-size-2.c
new file mode 100644
index 00000000000..fbf297302fc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Walloc-size-2.c
@@ -0,0 +1,20 @@
+/* Test that VLA types do not crash with -Walloc-size
+ { dg-do compile }
+ { dg-options "-Walloc-size" }
+ * */
+#include <stdlib.h>
+#include <alloca.h>
+
+struct foo { int x[10]; };
+
+void fo0(int n)
+{
+ struct foo (*p)[n] = malloc(sizeof *p);
+}
+
+void fo1(int n)
+{
+ struct bar { int x[n]; };
+ struct bar *p = malloc(sizeof *p);
+}
+
