Standardize concatenation macros

To create a token by concatenating already-defined macros and new
text, it's necessary to use multiple levels of macro.  We'd already
done that in several places in the code such as STM32_CAT; this now
standardizes it into a single place.

BUG=chrome-os-partner:18343
BRANCH=none
TEST=Build all platforms; examine ec.RO.map to see that irq_*_handler and prio_* symbols
     evaluated the same as before.  (Other macro evaluations would simply fail to compile
     if they were incorrect, since the concatenated tokens wouldn't fully expand.)

Change-Id: Ic9bf11d27881a84507fe7b6096dab6217c6c6dc7
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/63231
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/common.h b/include/common.h
index 1fb4fc5563..c6eeb11fef 100644
--- a/include/common.h
+++ b/include/common.h
@@ -10,6 +10,23 @@
 
 #include <stdint.h>
 
+/*
+ * Macros to concatenate 2 - 4 tokens together to form a single token.
+ * Multiple levels of nesting are required to convince the preprocessor to
+ * expand currently-defined tokens before concatenation.
+ *
+ * For example, if you have
+ *     #define FOO 1
+ *     #define BAR1 42
+ * Then
+ *     #define BAZ CONCAT2(BAR, FOO)
+ * Will evaluate to BAR1, which then evaluates to 42.
+ */
+#define CONCAT_STAGE_1(w, x, y, z) w ## x ## y ## z
+#define CONCAT2(w, x) CONCAT_STAGE_1(w, x, , )
+#define CONCAT3(w, x, y) CONCAT_STAGE_1(w, x, y, )
+#define CONCAT4(w, x, y, z) CONCAT_STAGE_1(w, x, y, z)
+
 /* Macros to access registers */
 #define REG32(addr) (*(volatile uint32_t *)(addr))
 #define REG16(addr) (*(volatile uint16_t *)(addr))