On 17.11.18 01:38, Giulio Moro via Xenomai wrote:
I have clang 3.9.1 (on Debian Stretch) on armv7.
the below minimal program clz-test.c:
```
#include <stdlib.h>
#include <arm_acle.h>
int main()
{
return __clz(0);
}
```
will fail to build when compiled with
`clang -I/usr/xenomai/include/cobalt -I/usr/xenomai/include clz-test.c` , as
follows:
```
In file included from test-clz.c:2:
/usr/lib/llvm-3.9/bin/../lib/clang/3.9.1/include/arm_acle.h:142:1: error:
expected identifier or '('
__clz(uint32_t __t) {
^
/usr/xenomai/include/boilerplate/compiler.h:87:3: note: expanded from macro
'__clz'
({ \
^
In file included from test-clz.c:2:
/usr/lib/llvm-3.9/bin/../lib/clang/3.9.1/include/arm_acle.h:142:1: error:
expected ')'
/usr/xenomai/include/boilerplate/compiler.h:87:3: note: expanded from macro
'__clz'
({ \
^
/usr/lib/llvm-3.9/bin/../lib/clang/3.9.1/include/arm_acle.h:142:1: note: to
match this '('
/usr/xenomai/include/boilerplate/compiler.h:87:2: note: expanded from macro
'__clz'
({ \
^
2 errors generated.
```
(compiler.h is included indirectly by `stdlib.h`)
This is because clang provides a definition of __clz as an inline function in
/usr/lib/llvm-3.9/lib/clang/3.9.1/include/arm_acle.h :
static __inline__ uint32_t __attribute__((__always_inline__, __nodebug__))
__clz(uint32_t __t) {
return __builtin_clz(__t);
}
however, xenomai-3/include/boilerplate/compiler.h defines __clz() as a macro,
hence the issue.
Note that compiler.h similarly defines a macro for __ctz , but that is not
defined in clang's arm_acle.h, so no issue with that one.
The patch below addresses the issue, leveraging clang's `__has_builtin()`
feature, while keeping things the same for gcc:
diff --git a/include/boilerplate/compiler.h b/include/boilerplate/compiler.h
index bcef7d4cc..8697a24b0 100644
--- a/include/boilerplate/compiler.h
+++ b/include/boilerplate/compiler.h
@@ -83,6 +83,15 @@ void __invalid_operand_size(void);
__ret; \
})
+#ifdef __clang__
+#if __has_builtin(__builtin_clz)
+#define DONT_DEF_CLZ
+#endif /* has_builtin */
+#endif /* __clang_ */
+
+#ifdef DONT_DEF_CLZ
+#undef DONT_DEF_CLZ
+#else /* DONT_DEF_CLZ */
#define __clz(__v) \
({ \
int __ret; \
@@ -101,6 +110,7 @@ void __invalid_operand_size(void);
} \
__ret; \
})
+#endif /* DONT_DEF_CLZ */
#ifdef __cplusplus
}
We should do
#define __clz __clz
in the clang case and then
#ifndef __clz
That should save some boilerplate code. Could you send a proper patch (see
CONTRIBUTING.md)?
Thanks!
Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
