The TYPE_MAIN_VARIANT() here was, for casts to a typedef'd type name,
resulting in all information about the typedef's involvement getting
lost. This drops necessary information for warnings and can make them
confusing or even misleading. It also makes specialized warnings for
unspecified-size system types (pid_t, uid_t, ...) impossible.
gcc/c/ChangeLog:
2021-03-09 David Lamparter <equi...@diac24.net>
PR c/99526
* c-typeck.c (build_c_cast): retain (unqualified) typedefs in
casts rather than stripping down to basic type.
---
gcc/c/c-typeck.c | 37 ++++++++++++++++++++++++++---
gcc/testsuite/gcc.dg/cast-typedef.c | 29 ++++++++++++++++++++++
2 files changed, 63 insertions(+), 3 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/cast-typedef.c
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 4e6d369c4c9c..7323a8e82547 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -5816,6 +5816,7 @@ c_safe_function_type_cast_p (tree t1, tree t2)
tree
build_c_cast (location_t loc, tree type, tree expr)
{
+ tree res_type, walk_type;
tree value;
bool int_operands = EXPR_INT_CONST_OPERANDS (expr);
@@ -5836,7 +5837,37 @@ build_c_cast (location_t loc, tree type, tree expr)
if (objc_is_object_ptr (type) && objc_is_object_ptr (TREE_TYPE (expr)))
return build1 (NOP_EXPR, type, expr);
+ /* Want to keep typedef information, but at the same time we need to strip
+ qualifiers for a proper rvalue. Unfortunately, we don't know if any
+ qualifiers on a typedef are part of the typedef or were locally supplied.
+ So grab the original typedef and use that only if it has no qualifiers.
+ cf. cast-typedef testcase */
+
+ res_type = NULL;
+ walk_type = type;
+
+ while (walk_type && TYPE_NAME (walk_type)
+ && TREE_CODE (TYPE_NAME (walk_type)) == TYPE_DECL)
+ {
+ tree orig_decl = lookup_name (TYPE_IDENTIFIER (walk_type));
+
+ if (!orig_decl || TREE_CODE (orig_decl) != TYPE_DECL)
+ break;
+
+ walk_type = TREE_TYPE (orig_decl);
+ if (TYPE_QUALS (walk_type) == TYPE_UNQUALIFIED)
+ {
+ res_type = walk_type;
+ break;
+ }
+
+ walk_type = DECL_ORIGINAL_TYPE (TYPE_NAME (walk_type));
+ }
+
type = TYPE_MAIN_VARIANT (type);
+ if (!res_type)
+ res_type = type;
+ gcc_assert (TYPE_MAIN_VARIANT (res_type) == type);
if (TREE_CODE (type) == ARRAY_TYPE)
{
@@ -5864,7 +5895,7 @@ build_c_cast (location_t loc, tree type, tree expr)
"ISO C forbids casting nonscalar to the same type");
/* Convert to remove any qualifiers from VALUE's type. */
- value = convert (type, value);
+ value = convert (res_type, value);
}
else if (TREE_CODE (type) == UNION_TYPE)
{
@@ -6018,7 +6049,7 @@ build_c_cast (location_t loc, tree type, tree expr)
" from %qT to %qT", otype, type);
ovalue = value;
- value = convert (type, value);
+ value = convert (res_type, value);
/* Ignore any integer overflow caused by the cast. */
if (TREE_CODE (value) == INTEGER_CST && !FLOAT_TYPE_P (otype))
@@ -6054,7 +6085,7 @@ build_c_cast (location_t loc, tree type, tree expr)
&& INTEGRAL_TYPE_P (TREE_TYPE (expr)))
|| TREE_CODE (expr) == REAL_CST
|| TREE_CODE (expr) == COMPLEX_CST)))
- value = build1 (NOP_EXPR, type, value);
+ value = build1 (NOP_EXPR, res_type, value);
/* If the expression has integer operands and so can occur in an
unevaluated part of an integer constant expression, ensure the
diff --git a/gcc/testsuite/gcc.dg/cast-typedef.c b/gcc/testsuite/gcc.dg/cast-typedef.c
new file mode 100644
index 000000000000..488624c16f72
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cast-typedef.c
@@ -0,0 +1,29 @@
+/* Test cast <> typedef interactions */
+/* Origin: David Lamparter <equi...@diac24.net> */
+/* { dg-do compile } */
+/* { dg-options "-Wconversion" } */
+
+typedef int typedefname;
+typedef volatile int qual1;
+typedef volatile typedefname qual2;
+
+extern int val;
+extern void f2(unsigned char arg);
+
+void
+f (void)
+{
+ /* -Wconversion just used to print out the actual type */
+
+ f2 ((typedefname) val); /* { dg-warning "typedefname" } */
+ f2 ((volatile typedefname) val); /* { dg-warning "typedefname" } */
+ f2 ((qual1) val); /* { dg-warning "int" } */
+ f2 ((qual2) val); /* { dg-warning "typedefname" } */
+
+ /* { dg-bogus "volatile" "qualifiers should be stripped" { target { "*-*-*" } } 19 } */
+ /* { dg-bogus "volatile" "qualifiers should be stripped" { target { "*-*-*" } } 20 } */
+ /* { dg-bogus "volatile" "qualifiers should be stripped" { target { "*-*-*" } } 21 } */
+
+ /* { dg-bogus "qual1" "typedef with qualifier should not be used" { target { "*-*-*" } } 20 } */
+ /* { dg-bogus "qual2" "typedef with qualifier should not be used" { target { "*-*-*" } } 21 } */
+}
