On 4/1/26 19:01, Sean Christopherson wrote:
On Tue, Mar 31, 2026, Shuah Khan wrote:
On 3/25/26 12:47, Hisam Mehboob wrote:
On 3/25/26 23:03, Shuah Khan wrote:
On 3/24/26 12:02, Shuah Khan wrote:
On 3/18/26 18:08, Hisam Mehboob wrote:
The backtrace() function and execinfo.h are GNU extensions available
in glibc but not in non-glibc C libraries such as musl. Building KVM
selftests with musl-gcc fails with:
lib/assert.c:9:10: fatal error: execinfo.h: No such file or directory
Guard the inclusion of execinfo.h under #ifdef __GLIBC__, and wrap
all backtrace() usage under the same guard with a fallback message
for non-glibc builds indicating that stack traces are not available.
Unlike the approach of adding a weak stub for backtrace(), this
explicitly handles the non-glibc case rather than silently providing
an empty implementation.
Link: https://lore.kernel.org/kvm/20250829142556.72577-7- [email protected]/
Suggested-by: Aqib Faruqui <[email protected]>
Signed-off-by: Hisam Mehboob <[email protected]>
---
tools/testing/selftests/kvm/lib/assert.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/tools/testing/selftests/kvm/lib/assert.c b/tools/
testing/selftests/kvm/lib/assert.c
index b49690658c60..3442b80c37c1 100644
--- a/tools/testing/selftests/kvm/lib/assert.c
+++ b/tools/testing/selftests/kvm/lib/assert.c
@@ -6,7 +6,9 @@
*/
#include "test_util.h"
+#ifdef __GLIBC__
#include <execinfo.h>
+#endif
Is __GLIBC__ defined in musl-gcc? Looks like that is the case with the
error?
If __GLIBC__ isn't there you shouldn't see this error because the include
is in - this error doesn't make sense if __GLIBC__ isn't defined. What
am I missing?
To clarify the compiler error you mentioned: the error log in the commit
message shows the failure that occurs before this patch is applied. Because
musl-gcc doesn't define __GLIBC__, the original unconditional <execinfo.h>
inclusion causes the build to fail. The #ifdef in my patch was intended to
fix that exact failure.
+#ifdef __GLIBC__
#include <execinfo.h>
+#endif
Also check tools/testing/selftests/bpf/test_progs.c - I think backtrace()
stub needs be defined only for the !__GLIBC__ case
Looking at how bpf/test_progs.c handles it, I agree the weak stub approach
is much cleaner. I will implement it so that it still prints an explicit
warning message when a trace is unavailable.
I disagree. _If_ we didn't need the __GLIBC__ #ifdef, then I would be in favor
of __weak, but since the #ifdeffery is needed, using an #ifdef and a __weak
symbol
is double the ugliness.
IMO, the way to make this less ugly is to using a single #ifdef and a local
stub.
diff --git a/tools/testing/selftests/kvm/lib/assert.c
b/tools/testing/selftests/kvm/lib/assert.c
index b49690658c60..315175ca49f1 100644
--- a/tools/testing/selftests/kvm/lib/assert.c
+++ b/tools/testing/selftests/kvm/lib/assert.c
@@ -6,11 +6,13 @@
*/
#include "test_util.h"
-#include <execinfo.h>
#include <sys/syscall.h>
#include "kselftest.h"
+#ifdef __GLIBC__
+#include <execinfo.h>
+
/* Dumps the current stack trace to stderr. */
static void __attribute__((noinline)) test_dump_stack(void);
static void test_dump_stack(void)
@@ -57,6 +59,9 @@ static void test_dump_stack(void)
system(cmd);
#pragma GCC diagnostic pop
}
+#else
+static void test_dump_stack(void) {}
+#endif
static pid_t _gettid(void)
{
Thanks for the suggestion. I will send a v2 implementing this approach.
