Hi!
The pr120057-1.c testcase is incorrectly rejected since
r15-4377 (and for a while it also ICEd after the error), i.e.
the optimization of large C initializers using RAW_DATA_CST.
Similarly, the embed-18.c testcase is incorrectly rejected since
the embed support has been introduced and RAW_DATA_CST used for that.
The callers of check_constexpr_init (store_init_value and
output_init_element) compute int_const_expr as
int_const_expr = (TREE_CODE (init) == INTEGER_CST
&& !TREE_OVERFLOW (init)
&& INTEGRAL_TYPE_P (TREE_TYPE (init)));
but that is only passed through down to check_constexpr_init.
I think tweaking those 2 callers to also allow RAW_DATA_CST for
int_const_expr when check_constexpr_init needs top special case it
no matter what would be larger, so the patch just changes
check_constexpr_init to deal with RAW_DATA_CST in the initializers.
For TYPE_UNSIGNED char precision integral types RAW_DATA_CST is
always valid, for !TYPE_UNSIGNED we need to check for 128-255 values
being turned into negative ones.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk and
15.2?
2025-05-02 Jakub Jelinek <ja...@redhat.com>
PR c/120057
* c-typeck.cc (check_constexpr_init): Handle RAW_DATA_CST.
* gcc.dg/cpp/embed-18.c: New test.
* gcc.dg/pr120057-1.c: New test.
* gcc.dg/pr120057-2.c: New test.
--- gcc/c/c-typeck.cc.jj 2025-05-02 09:11:56.000000000 +0200
+++ gcc/c/c-typeck.cc 2025-05-02 11:09:40.778819774 +0200
@@ -9143,8 +9143,24 @@ check_constexpr_init (location_t loc, tr
/* The initializer must be an integer constant expression,
representable in the target type. */
if (!int_const_expr)
- error_at (loc, "%<constexpr%> integer initializer is not an "
- "integer constant expression");
+ {
+ if (TREE_CODE (init) == RAW_DATA_CST
+ && TYPE_PRECISION (type) == CHAR_BIT)
+ {
+ if (!TYPE_UNSIGNED (type))
+ for (unsigned int i = 0;
+ i < (unsigned) RAW_DATA_LENGTH (init); ++i)
+ if (RAW_DATA_SCHAR_ELT (init, i) < 0)
+ {
+ error_at (loc, "%<constexpr%> initializer not "
+ "representable in type of object");
+ break;
+ }
+ }
+ else
+ error_at (loc, "%<constexpr%> integer initializer is not an "
+ "integer constant expression");
+ }
else if (!int_fits_type_p (init, type))
error_at (loc, "%<constexpr%> initializer not representable in "
"type of object");
--- gcc/testsuite/gcc.dg/cpp/embed-18.c.jj 2025-05-02 11:26:07.358600822
+0200
+++ gcc/testsuite/gcc.dg/cpp/embed-18.c 2025-05-02 11:26:49.642032817 +0200
@@ -0,0 +1,7 @@
+/* PR c/120057 */
+/* { dg-do compile } */
+/* { dg-options "-std=c23 --embed-dir=${srcdir}/c-c++-common/cpp/embed-dir" }
*/
+
+constexpr unsigned char magna_carta[] = {
+#embed <magna-carta.txt>
+};
--- gcc/testsuite/gcc.dg/pr120057-1.c.jj 2025-05-02 11:22:49.441259486
+0200
+++ gcc/testsuite/gcc.dg/pr120057-1.c 2025-05-02 11:22:24.952588444 +0200
@@ -0,0 +1,18 @@
+/* PR c/120057 */
+/* { dg-do compile } */
+/* { dg-options "-std=c23" } */
+
+constexpr char foo[65] = {
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1
+};
+constexpr char bar[66] = {
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1, 2
+};
--- gcc/testsuite/gcc.dg/pr120057-2.c.jj 2025-05-02 11:22:56.297167390
+0200
+++ gcc/testsuite/gcc.dg/pr120057-2.c 2025-05-02 11:24:57.635537429 +0200
@@ -0,0 +1,11 @@
+/* PR c/120057 */
+/* { dg-do compile } */
+/* { dg-options "-std=c23" } */
+
+constexpr signed char foo[65] = {
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 129, 11, 12, 13, 14, 15, 16, /* { dg-error
"'constexpr' initializer not representable in type of object" } */
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
+ 1
+};
Jakub
