Module Name: src
Committed By: rillig
Date: Sat Aug 27 23:24:37 UTC 2022
Modified Files:
src/tests/usr.bin/xlint/lint1: gcc_attribute_aligned.c
Log Message:
tests/lint: add more information to test for __attribute__((aligned))
Declaring an array type having a negative dimension is the simplest way
to embed an integer into a lint diagnostic, thereby revealing what size
and alignment lint has calculated for a struct.
While here, move these "compile-time assertions" closer to their
corresponding struct, to make reading easier.
To generate a diff of this commit:
cvs rdiff -u -r1.4 -r1.5 \
src/tests/usr.bin/xlint/lint1/gcc_attribute_aligned.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/tests/usr.bin/xlint/lint1/gcc_attribute_aligned.c
diff -u src/tests/usr.bin/xlint/lint1/gcc_attribute_aligned.c:1.4 src/tests/usr.bin/xlint/lint1/gcc_attribute_aligned.c:1.5
--- src/tests/usr.bin/xlint/lint1/gcc_attribute_aligned.c:1.4 Sat Aug 27 21:59:41 2022
+++ src/tests/usr.bin/xlint/lint1/gcc_attribute_aligned.c Sat Aug 27 23:24:37 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: gcc_attribute_aligned.c,v 1.4 2022/08/27 21:59:41 rillig Exp $ */
+/* $NetBSD: gcc_attribute_aligned.c,v 1.5 2022/08/27 23:24:37 rillig Exp $ */
# 3 "gcc_attribute_aligned.c"
/*
@@ -20,11 +20,22 @@ union fp_addr {
} fa_32;
} __attribute__((packed)) __attribute__((aligned(4)));
+/* Each variant of the union has size 8. */
+/* expect+1: error: negative array dimension (-8) [20] */
+typedef int sizeof_fp_addr[-(int)sizeof(union fp_addr)];
+
struct fpacc87 {
uint64_t f87_mantissa;
uint16_t f87_exp_sign;
} __attribute__((packed)) __attribute__((aligned(2)));
+/*
+ * Due to the 'packed', the uint64_t does not need to be aligned on an 8-byte
+ * boundary, which allows the struct to have the minimal required size of 10.
+ */
+/* expect+1: error: negative array dimension (-10) [20] */
+typedef int sizeof_fpacc87[-(int)sizeof(struct fpacc87)];
+
struct save87 {
uint16_t s87_cw __attribute__((aligned(4)));
uint16_t s87_sw __attribute__((aligned(4)));
@@ -34,15 +45,9 @@ struct save87 {
struct fpacc87 s87_ac[8];
};
-struct {
- unsigned int sizeof_fp_addr: sizeof(union fp_addr) == 8 ? 1 : -1;
-
- unsigned int sizeof_fpacc87: sizeof(struct fpacc87) == 10 ? 1 : -1;
-
- /* FIXME: @4 2 + @4 2 + @4 2 + @4 8 + @4 8 + @2 (8 * 10) == 108 */
- /* expect+1: error: illegal bit-field size: 255 [36] */
- unsigned int sizeof_save87: sizeof(struct save87) == 108 ? 1 : -1;
-};
+/* FIXME: @4 2 + @4 2 + @4 2 + @4 8 + @4 8 + @2 (8 * 10) == 108 */
+/* expect+1: error: negative array dimension (-104) [20] */
+typedef int sizeof_save87[-(int)sizeof(struct save87)];
void
@@ -53,7 +58,16 @@ aligned_struct_member(void)
int second __attribute__((__aligned__(16)));
};
- /* TODO: should be -20 instead of -8. */
+ /*
+ * Aligning 'second' to a 16-bytes boundary not only aligns the member
+ * inside the structure, it also affects the alignment requirement of
+ * the whole structure. Due to this struct alignment, the size of the
+ * structure gets rounded up to 32 instead of using the minimally
+ * necessary storage of 20.
+ *
+ * https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html
+ */
+ /* TODO: should be -32 instead of -8. */
/* expect+1: error: negative array dimension (-8) [20] */
typedef int ctassert[-(int)sizeof(struct aligned)];
}
