This patch adds two new attributes. The followup patch makes use of
the attributes in -fanalyzer.
gcc/c-family/ChangeLog:
* c-attribs.c (attr_noreturn_exclusions): Add
"returns_zero_on_failure" and "returns_zero_on_success".
(attr_returns_twice_exclusions): Likewise.
(attr_returns_zero_on_exclusions): New.
(c_common_attribute_table): Add "returns_zero_on_failure" and
"returns_zero_on_success".
(handle_returns_zero_on_attributes): New.
gcc/ChangeLog:
* doc/extend.texi (Common Function Attributes): Document
"returns_zero_on_failure" and "returns_zero_on_success".
gcc/testsuite/ChangeLog:
* c-c++-common/attr-returns-zero-on-1.c: New test.
Signed-off-by: David Malcolm <dmalc...@redhat.com>
---
gcc/c-family/c-attribs.c | 37 ++++++++++
gcc/doc/extend.texi | 16 +++++
.../c-c++-common/attr-returns-zero-on-1.c | 68 +++++++++++++++++++
3 files changed, 121 insertions(+)
create mode 100644 gcc/testsuite/c-c++-common/attr-returns-zero-on-1.c
diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index 100c2dabab2..9e03156de5e 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -153,6 +153,7 @@ static tree handle_argspec_attribute (tree *, tree, tree,
int, bool *);
static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
static tree handle_warn_unused_attribute (tree *, tree, tree, int, bool *);
static tree handle_returns_nonnull_attribute (tree *, tree, tree, int, bool *);
+static tree handle_returns_zero_on_attributes (tree *, tree, tree, int, bool
*);
static tree handle_omp_declare_simd_attribute (tree *, tree, tree, int,
bool *);
static tree handle_omp_declare_variant_attribute (tree *, tree, tree, int,
@@ -221,6 +222,8 @@ extern const struct attribute_spec::exclusions
attr_noreturn_exclusions[] =
ATTR_EXCL ("pure", true, true, true),
ATTR_EXCL ("returns_twice", true, true, true),
ATTR_EXCL ("warn_unused_result", true, true, true),
+ ATTR_EXCL ("returns_zero_on_failure", true, true, true),
+ ATTR_EXCL ("returns_zero_on_success", true, true, true),
ATTR_EXCL (NULL, false, false, false),
};
@@ -235,6 +238,8 @@ attr_warn_unused_result_exclusions[] =
static const struct attribute_spec::exclusions attr_returns_twice_exclusions[]
=
{
ATTR_EXCL ("noreturn", true, true, true),
+ ATTR_EXCL ("returns_zero_on_failure", true, true, true),
+ ATTR_EXCL ("returns_zero_on_success", true, true, true),
ATTR_EXCL (NULL, false, false, false),
};
@@ -275,6 +280,16 @@ static const struct attribute_spec::exclusions
attr_stack_protect_exclusions[] =
ATTR_EXCL (NULL, false, false, false),
};
+/* Exclusions that apply to the returns_zero_on_* attributes. */
+static const struct attribute_spec::exclusions
+ attr_returns_zero_on_exclusions[] =
+{
+ ATTR_EXCL ("noreturn", true, true, true),
+ ATTR_EXCL ("returns_twice", true, true, true),
+ ATTR_EXCL ("returns_zero_on_failure", true, true, true),
+ ATTR_EXCL ("returns_zero_on_success", true, true, true),
+ ATTR_EXCL (NULL, false, false, false),
+};
/* Table of machine-independent attributes common to all C-like languages.
@@ -493,6 +508,12 @@ const struct attribute_spec c_common_attribute_table[] =
handle_warn_unused_attribute, NULL },
{ "returns_nonnull", 0, 0, false, true, true, false,
handle_returns_nonnull_attribute, NULL },
+ { "returns_zero_on_failure",0, 0, false, true, true, false,
+ handle_returns_zero_on_attributes,
+ attr_returns_zero_on_exclusions },
+ { "returns_zero_on_success",0, 0, false, true, true, false,
+ handle_returns_zero_on_attributes,
+ attr_returns_zero_on_exclusions },
{ "omp declare simd", 0, -1, true, false, false, false,
handle_omp_declare_simd_attribute, NULL },
{ "omp declare variant base", 0, -1, true, false, false, false,
@@ -5660,6 +5681,22 @@ handle_returns_nonnull_attribute (tree *node, tree name,
tree, int,
return NULL_TREE;
}
+/* Handle "returns_zero_on_failure" and "returns_zero_on_success" attributes;
+ arguments as in struct attribute_spec.handler. */
+
+static tree
+handle_returns_zero_on_attributes (tree *node, tree name, tree, int,
+ bool *no_add_attrs)
+{
+ if (!INTEGRAL_TYPE_P (TREE_TYPE (*node)))
+ {
+ error ("%qE attribute on a function not returning an integral type",
+ name);
+ *no_add_attrs = true;
+ }
+ return NULL_TREE;
+}
+
/* Handle a "designated_init" attribute; arguments as in
struct attribute_spec.handler. */
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index e9f47519df2..5a6ef464779 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -3784,6 +3784,22 @@ function. Examples of such functions are @code{setjmp}
and @code{vfork}.
The @code{longjmp}-like counterpart of such function, if any, might need
to be marked with the @code{noreturn} attribute.
+@item returns_zero_on_failure
+@cindex @code{returns_zero_on_failure} function attribute
+The @code{returns_zero_on_failure} attribute hints that the function
+can succeed or fail, returning non-zero on success and zero on failure.
+This is used by the @option{-fanalyzer} option to consider both outcomes
+separately, which may improve how it explores error-handling paths, and
+how such outcomes are labelled in diagnostics. It is also a hint
+to the human reader of the source code.
+
+@item returns_zero_on_success
+@cindex @code{returns_zero_on_success} function attribute
+The @code{returns_zero_on_success} attribute is identical to the
+@code{returns_zero_on_failure} attribute, apart from having the
+opposite interpretation of the return value: zero on success, non-zero
+on failure.
+
@item section ("@var{section-name}")
@cindex @code{section} function attribute
@cindex functions in arbitrary sections
diff --git a/gcc/testsuite/c-c++-common/attr-returns-zero-on-1.c
b/gcc/testsuite/c-c++-common/attr-returns-zero-on-1.c
new file mode 100644
index 00000000000..5475dfe61db
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/attr-returns-zero-on-1.c
@@ -0,0 +1,68 @@
+/* Verify the parsing of the "returns_zero_on_{sucess|failure}" attributes. */
+
+/* Correct usage. */
+
+extern int test_int_return_s ()
+ __attribute__((returns_zero_on_success));
+extern long test_long_return_f ()
+ __attribute__((returns_zero_on_failure));
+
+/* Should complain if not a function. */
+
+extern int not_a_function_s
+ __attribute__((returns_zero_on_success)); /* { dg-warning
"'returns_zero_on_success' attribute only applies to function types" } */
+extern int not_a_function_f
+ __attribute__((returns_zero_on_failure)); /* { dg-warning
"'returns_zero_on_failure' attribute only applies to function types" } */
+
+/* Should complain if return type is not integral. */
+
+extern void test_void_return_s ()
+ __attribute__((returns_zero_on_success)); /* { dg-error
"'returns_zero_on_success' attribute on a function not returning an integral
type" } */
+extern void test_void_return_f ()
+ __attribute__((returns_zero_on_failure)); /* { dg-error
"'returns_zero_on_failure' attribute on a function not returning an integral
type" } */
+
+extern void *test_void_star_return_s ()
+ __attribute__((returns_zero_on_success)); /* { dg-error
"'returns_zero_on_success' attribute on a function not returning an integral
type" } */
+extern void *test_void_star_return_f ()
+ __attribute__((returns_zero_on_failure)); /* { dg-error
"'returns_zero_on_failure' attribute on a function not returning an integral
type" } */
+
+/* (and this prevents mixing with returns_non_null, which requires a pointer).
*/
+
+/* Should complain if more than one returns_* attribute. */
+
+extern int test_void_returns_s_f ()
+ __attribute__((returns_zero_on_success))
+ __attribute__((returns_zero_on_failure)); /* { dg-warning "ignoring
attribute 'returns_zero_on_failure' because it conflicts with attribute
'returns_zero_on_success'" } */
+extern int test_void_returns_f_s ()
+ __attribute__((returns_zero_on_failure))
+ __attribute__((returns_zero_on_success)); /* { dg-warning "ignoring
attribute 'returns_zero_on_success' because it conflicts with attribute
'returns_zero_on_failure'" } */
+
+/* Should complain if mixed with "noreturn". */
+
+extern int test_noreturn_returns_s ()
+ __attribute__((noreturn))
+ __attribute__((returns_zero_on_success)); /* { dg-warning "ignoring
attribute 'returns_zero_on_success' because it conflicts with attribute
'noreturn'" } */
+extern int test_returns_s_noreturn ()
+ __attribute__((returns_zero_on_success))
+ __attribute__((noreturn)); /* { dg-warning "ignoring attribute 'noreturn'
because it conflicts with attribute 'returns_zero_on_success'" } */
+extern int test_noreturn_returns_f ()
+ __attribute__((noreturn))
+ __attribute__((returns_zero_on_failure)); /* { dg-warning "ignoring
attribute 'returns_zero_on_failure' because it conflicts with attribute
'noreturn'" } */
+extern int test_returns_f_noreturn ()
+ __attribute__((returns_zero_on_failure))
+ __attribute__((noreturn)); /* { dg-warning "ignoring attribute 'noreturn'
because it conflicts with attribute 'returns_zero_on_failure'" } */
+
+/* Should complain if mixed with "returns_twice". */
+
+extern int test_returns_twice_returns_s ()
+ __attribute__((returns_twice))
+ __attribute__((returns_zero_on_success)); /* { dg-warning "ignoring
attribute 'returns_zero_on_success' because it conflicts with attribute
'returns_twice'" } */
+extern int test_returns_s_returns_twice ()
+ __attribute__((returns_zero_on_success))
+ __attribute__((returns_twice)); /* { dg-warning "ignoring attribute
'returns_twice' because it conflicts with attribute 'returns_zero_on_success'"
} */
+extern int test_returns_twice_returns_f ()
+ __attribute__((returns_twice))
+ __attribute__((returns_zero_on_failure)); /* { dg-warning "ignoring
attribute 'returns_zero_on_failure' because it conflicts with attribute
'returns_twice'" } */
+extern int test_returns_f_returns_twice ()
+ __attribute__((returns_zero_on_failure))
+ __attribute__((returns_twice)); /* { dg-warning "ignoring attribute
'returns_twice' because it conflicts with attribute 'returns_zero_on_failure'"
} */
--
2.26.3
