On 16/03/2022 12.15, Halil Pasic wrote:
On Wed, 16 Mar 2022 11:28:59 +0100
Thomas Huth <thuth@xxxxxxxxxx> wrote:
On 16/03/2022 10.53, marcandre.lureau@xxxxxxxxxx wrote:
From: Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>
Replace a config-time define with a compile time condition
define (compatible with clang and gcc) that must be declared prior to
its usage. This avoids having a global configure time define, but also
prevents from bad usage, if the config header wasn't included before.
This can help to make some code independent from qemu too.
gcc supports __BYTE_ORDER__ from about 4.6 and clang from 3.2.
Signed-off-by: Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>
---
[...]
@@ -188,7 +188,7 @@ CPU_CONVERT(le, 64, uint64_t)
* a compile-time constant if you pass in a constant. So this can be
* used to initialize static variables.
*/
-#if defined(HOST_WORDS_BIGENDIAN)
+#if HOST_BIG_ENDIAN
# define const_le32(_x) \
((((_x) & 0x000000ffU) << 24) | \
(((_x) & 0x0000ff00U) << 8) | \
@@ -211,7 +211,7 @@ typedef union {
typedef union {
float64 d;
-#if defined(HOST_WORDS_BIGENDIAN)
+#if HOST_BIG_ENDIAN
struct {
uint32_t upper;
uint32_t lower;
@@ -235,7 +235,7 @@ typedef union {
typedef union {
float128 q;
-#if defined(HOST_WORDS_BIGENDIAN)
+#if HOST_BIG_ENDIAN
struct {
uint32_t upmost;
uint32_t upper;
diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 0a5e67fb970e..7fdd88adb368 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -7,6 +7,8 @@
#ifndef COMPILER_H
#define COMPILER_H
+#define HOST_BIG_ENDIAN (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
Why don't you do it this way instead:
#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#define HOST_WORDS_BIGENDIAN 1
#endif
... that way you could avoid the churn in all the other files?
I guess "prevents from bad usage, if the config header wasn't included
before" from the commit message is the answer to that question. I agree
that it is more robust. If we keep the #if defined we really can't
differentiate between "not defined because not big-endian" and "not
defined because the appropriate header was not included."
Ok, fair point, now I got it.
Acked-by: Thomas Huth <thuth@xxxxxxxxxx>
