>
> C programmers increasingly use static to indicate that
> pointer parameters are non-null. Clang can exploit this
> for warnings and optimizations. GCC has some warnings
> but not all warnings it has for nonnull. Below is a
> patch to add a nonnull attribute automatically for such
> arguments and to remove the special and more limited
> nonnull warnings for static. This patch found some
> misplaced annotations in one of my projects via
> -Wnonnull-compare which clang does not seem to have,
> so I think this could be useful.
c: Synthesize nonnull attribute for parameters declared with static
[PR110815]
Parameters declared with `static` are nonnull. We synthesize
an artifical nonnull attribute for such parameters to get the
same warnings and optimizations.
Bootstrapped and regression tested on x86.
PR c/102558
PR 102556
PR c/110815
gcc/c-family:
* c-attribs.cc (build_attr_access_from_parms): Synthesize
nonnull attribute for parameters declared with `static`.
gcc:
* gimple-ssa-warn-access.cc
(pass_waccess::maybe_check_access_sizes):
remove warning for parameters declared with `static`.
gcc/testsuite:
* gcc.dg/Wnonnull-8.c: Adapt test.
* gcc.dg/Wnonnull-9.c: New test.
diff --git a/gcc/c-family/c-attribs.cc b/gcc/c-family/c-attribs.cc
index e2792ca6898..ae7ffeb1f65 100644
--- a/gcc/c-family/c-attribs.cc
+++ b/gcc/c-family/c-attribs.cc
@@ -5280,6 +5280,7 @@ build_attr_access_from_parms (tree parms, bool
skip_voidptr)
arg2pos.put (arg, argpos);
}
+ tree nnlist = NULL_TREE;
argpos = 0;
for (tree arg = parms; arg; arg = TREE_CHAIN (arg), ++argpos)
{
@@ -5313,6 +5314,11 @@ build_attr_access_from_parms (tree parms, bool
skip_voidptr)
tree str = TREE_VALUE (argspec);
const char *s = TREE_STRING_POINTER (str);
+ /* Collect the list of nonnull arguments which use "[static ..]". */
+ if (s != NULL && s[0] == '[' && s[1] == 's')
+ nnlist = tree_cons (NULL_TREE, build_int_cst (integer_type_node,
+ argpos + 1), nnlist);
+
/* Create the attribute access string from the arg spec string,
optionally followed by position of the VLA bound argument if
it is one. */
@@ -5380,6 +5386,10 @@ build_attr_access_from_parms (tree parms, bool
skip_voidptr)
if (!spec.length ())
return NULL_TREE;
+ /* If we have nonnull arguments, synthesize an attribute. */
+ if (nnlist != NULL_TREE)
+ nnlist = build_tree_list (get_identifier ("nonnull"), nnlist);
+
/* Attribute access takes a two or three arguments. Wrap VBLIST in
another list in case it has more nodes than would otherwise fit. */
vblist = build_tree_list (NULL_TREE, vblist);
@@ -5390,7 +5400,7 @@ build_attr_access_from_parms (tree parms, bool
skip_voidptr)
tree str = build_string (spec.length (), spec.c_str ());
tree attrargs = tree_cons (NULL_TREE, str, vblist);
tree name = get_identifier ("access");
- return build_tree_list (name, attrargs);
+ return tree_cons (name, attrargs, nnlist);
}
/* Handle a "nothrow" attribute; arguments as in
diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc
index b70d67dc47b..b8e89d01088 100644
--- a/gcc/gimple-ssa-warn-access.cc
+++ b/gcc/gimple-ssa-warn-access.cc
@@ -3491,16 +3491,6 @@ pass_waccess::maybe_check_access_sizes (rdwr_map *rwm,
tree fndecl, tree fntype,
ptridx + 1, sizidx + 1, sizstr))
arg_warned = OPT_Wnonnull;
}
- else if (access_size && access.second.static_p)
- {
- /* Warn about null pointers for [static N] array arguments
- but do not warn for ordinary (i.e., nonstatic) arrays. */
- if (warning_at (loc, OPT_Wnonnull,
- "argument %i to %<%T[static %E]%> "
- "is null where non-null expected",
- ptridx + 1, argtype, access_nelts))
- arg_warned = OPT_Wnonnull;
- }
if (arg_warned != no_warning)
{
diff --git a/gcc/testsuite/gcc.dg/Wnonnull-8.c
b/gcc/testsuite/gcc.dg/Wnonnull-8.c
index 02871a76689..b24fd67cebc 100644
--- a/gcc/testsuite/gcc.dg/Wnonnull-8.c
+++ b/gcc/testsuite/gcc.dg/Wnonnull-8.c
@@ -10,5 +10,5 @@ foo (int a[static 7])
int
main ()
{
- foo ((int *) 0); /* { dg-warning "argument 1 to 'int\\\[static 7\\\]' is
null where non-null expected" } */
+ foo ((int *) 0); /* { dg-warning "argument 1 null where non-null
expected" } */
}
diff --git a/gcc/testsuite/gcc.dg/Wnonnull-9.c
b/gcc/testsuite/gcc.dg/Wnonnull-9.c
new file mode 100644
index 00000000000..1c57eefd2ae
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wnonnull-9.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+
+void
+foo (int a[static 1])
+{
+ if ((void*)0 == a) /* { dg-warning "argument" "compared to NULL" } */
+ return;
+}
+
+int
+main ()
+{
+ foo ((void*)0); /* { dg-warning "argument 1 null where non-null
expected" } */
+}
+
