[PATCH liburing v1 0/3] Fix Compilation Error on Android and Some Cleanup

[PATCH liburing v1 0/3] Fix Compilation Error on Android and Some Cleanup

[Ammar Faizi]

Hi Jens,

Another day in the thrilling world of cross-platform compatibility...

Alviro discovered that some Android versions are missing `aligned_alloc()`
in `<stdlib.h>`, leading to a compilation error on Termux 0.118.0:

```
cmd-discard.c:383:11: warning: call to undeclared library function \
'aligned_alloc' with type 'void *(unsigned long, unsigned long)'; ISO \
C99 and later do not support implicit function declarations \
[-Wimplicit-function-declaration]

        buffer = aligned_alloc(lba_size, lba_size);
                 ^
```

To resolve this without rewriting large portions of liburing tests,
introduce a helper function that wraps `posix_memalign()` and provides
our own `aligned_alloc()`.

While we're at it, there's a redundant double negation lurking in
`liburing.h`. Let's clean that up too.  

Also, to prevent yet another round of confusion like what happened in
PR #1336, document the history of `io_uring_get_sqe()` in the header
file.

Ref: https://github.com/axboe/liburing/pull/1336

Signed-off-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---

Ammar Faizi (3):
  liburing.h: Remove redundant double negation
  liburing.h: Explain the history of `io_uring_get_sqe()`
  Fix missing `aligned_alloc()` on some Android devices

 examples/helpers.c     | 10 ++++++++++
 examples/helpers.h     |  7 +++++++
 examples/reg-wait.c    |  2 ++
 src/include/liburing.h | 21 ++++++++++++++++++++-
 test/helpers.c         | 10 ++++++++++
 test/helpers.h         |  8 ++++++++
 6 files changed, 57 insertions(+), 1 deletion(-)


base-commit: 66b071d1470ae787d47d4cb8d9cb3836249baf61
-- 
Ammar Faizi

[PATCH liburing v1 1/3] liburing.h: Remove redundant double negation

[Ammar Faizi]

The `enabled` variable is already a boolean, so applying the negation
operator twice has no effect. Remove it to improves clarity and
simplicity.

Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---
 src/include/liburing.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/include/liburing.h b/src/include/liburing.h
index 6393599cb3bf..b2d76f3224e2 100644
--- a/src/include/liburing.h
+++ b/src/include/liburing.h
@@ -1410,25 +1410,25 @@ IOURINGINLINE bool io_uring_cq_eventfd_enabled(const struct io_uring *ring)
 	return !(*ring->cq.kflags & IORING_CQ_EVENTFD_DISABLED);
 }
 
 /*
  * Toggle eventfd notification on or off, if an eventfd is registered with
  * the ring.
  */
 IOURINGINLINE int io_uring_cq_eventfd_toggle(struct io_uring *ring,
 					     bool enabled)
 {
 	uint32_t flags;
 
-	if (!!enabled == io_uring_cq_eventfd_enabled(ring))
+	if (enabled == io_uring_cq_eventfd_enabled(ring))
 		return 0;
 
 	if (!ring->cq.kflags)
 		return -EOPNOTSUPP;
 
 	flags = *ring->cq.kflags;
 
 	if (enabled)
 		flags &= ~IORING_CQ_EVENTFD_DISABLED;
 	else
 		flags |= IORING_CQ_EVENTFD_DISABLED;
 
-- 
Ammar Faizi

[PATCH liburing v1 2/3] liburing.h: Explain the history of `io_uring_get_sqe()`

[Ammar Faizi]

Add a comment for `io_uring_get_sqe()` to provide historical context
and prevent misunderstandings, as seen in Pull Request 1336.

Link: https://github.com/axboe/liburing/pull/1336
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---
 src/include/liburing.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/include/liburing.h b/src/include/liburing.h
index b2d76f3224e2..98419e378f72 100644
--- a/src/include/liburing.h
+++ b/src/include/liburing.h
@@ -1622,24 +1622,43 @@ IOURINGINLINE int io_uring_buf_ring_available(struct io_uring *ring,
 					      unsigned short bgid)
 {
 	uint16_t head;
 	int ret;
 
 	ret = io_uring_buf_ring_head(ring, bgid, &head);
 	if (ret)
 		return ret;
 
 	return (uint16_t) (br->tail - head);
 }
 
+/*
+ * As of liburing-2.2, io_uring_get_sqe() has been converted into a
+ * "static inline" function. However, this change breaks seamless
+ * updates of liburing.so, as applications would need to be recompiled.
+ * To ensure backward compatibility, liburing keeps the original
+ * io_uring_get_sqe() symbol available in the shared library.
+ *
+ * To accomplish this, io_uring_get_sqe() is defined as a non-static
+ * inline function when LIBURING_INTERNAL is set, which only applies
+ * during liburing.so builds.
+ *
+ * This strategy ensures new users adopt the "static inline" version
+ * while preserving compatibility for old applications linked against
+ * the shared library.
+ *
+ * Relevant commits:
+ * 8be8af4afcb4 ("queue: provide io_uring_get_sqe() symbol again")
+ * 52dcdbba35c8 ("src/queue: protect io_uring_get_sqe() with LIBURING_INTERNAL")
+ */
 #ifndef LIBURING_INTERNAL
 IOURINGINLINE struct io_uring_sqe *io_uring_get_sqe(struct io_uring *ring)
 {
 	return _io_uring_get_sqe(ring);
 }
 #else
 struct io_uring_sqe *io_uring_get_sqe(struct io_uring *ring);
 #endif
 
 ssize_t io_uring_mlock_size(unsigned entries, unsigned flags);
 ssize_t io_uring_mlock_size_params(unsigned entries, struct io_uring_params *p);
 
-- 
Ammar Faizi

[PATCH liburing v1 3/3] Fix missing `aligned_alloc()` on some Android devices

[Ammar Faizi]

Some Android versions lack `aligned_alloc()` in `<stdlib.h>`. Compiling
on Termux 0.118.0 yields this error:

```
cmd-discard.c:383:11: warning: call to undeclared library function \
'aligned_alloc' with type 'void *(unsigned long, unsigned long)'; ISO \
C99 and later do not support implicit function declarations \
[-Wimplicit-function-declaration]

        buffer = aligned_alloc(lba_size, lba_size);
                 ^
```

To avoid making large changes in tests, define a helper function that
wraps `posix_memalign()` as our own `aligned_alloc()`.

Just another day of working around platform quirks.

Co-authored-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Signed-off-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
---
 examples/helpers.c  | 10 ++++++++++
 examples/helpers.h  |  7 +++++++
 examples/reg-wait.c |  2 ++
 test/helpers.c      | 10 ++++++++++
 test/helpers.h      |  8 ++++++++
 5 files changed, 37 insertions(+)

diff --git a/examples/helpers.c b/examples/helpers.c
index b70ce7c1f314..59b31ecb4aeb 100644
--- a/examples/helpers.c
+++ b/examples/helpers.c
@@ -51,12 +51,22 @@ int setup_listening_socket(int port, int ipv6)
 	if (ret < 0) {
 		perror("bind()");
 		return -1;
 	}
 
 	if (listen(fd, 1024) < 0) {
 		perror("listen()");
 		return -1;
 	}
 
 	return fd;
 }
+
+void *aligned_alloc(size_t alignment, size_t size)
+{
+	void *ret;
+
+	if (posix_memalign(&ret, alignment, size))
+		return NULL;
+
+	return ret;
+}
diff --git a/examples/helpers.h b/examples/helpers.h
index 9b1cf34f9b0d..d73ee4a5bc1a 100644
--- a/examples/helpers.h
+++ b/examples/helpers.h
@@ -1,7 +1,14 @@
 /* SPDX-License-Identifier: MIT */
 #ifndef LIBURING_EX_HELPERS_H
 #define LIBURING_EX_HELPERS_H
 
 int setup_listening_socket(int port, int ipv6);
 
+/*
+ * Some Android versions lack aligned_alloc in stdlib.h.
+ * To avoid making large changes in tests, define a helper
+ * function that wraps posix_memalign as our own aligned_alloc.
+ */
+void *aligned_alloc(size_t alignment, size_t size);
+
 #endif
diff --git a/examples/reg-wait.c b/examples/reg-wait.c
index 0e119aaf4f03..ff61b8d10387 100644
--- a/examples/reg-wait.c
+++ b/examples/reg-wait.c
@@ -4,24 +4,26 @@
  *
  * (C) 2024 Jens Axboe <axboe@kernel.dk>
  */
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <assert.h>
 #include <sys/time.h>
 #include <liburing.h>
 
+#include "helpers.h"
+
 static unsigned long long mtime_since(const struct timeval *s,
 				      const struct timeval *e)
 {
 	long long sec, usec;
 
 	sec = e->tv_sec - s->tv_sec;
 	usec = (e->tv_usec - s->tv_usec);
 	if (sec > 0 && usec < 0) {
 		sec--;
 		usec += 1000000;
 	}
 
diff --git a/test/helpers.c b/test/helpers.c
index e84aaa7aee15..0718691174de 100644
--- a/test/helpers.c
+++ b/test/helpers.c
@@ -354,12 +354,22 @@ unsigned long long utime_since(const struct timeval *s, const struct timeval *e)
 
 	sec *= 1000000;
 	return sec + usec;
 }
 
 unsigned long long utime_since_now(struct timeval *tv)
 {
 	struct timeval end;
 
 	gettimeofday(&end, NULL);
 	return utime_since(tv, &end);
 }
+
+void *aligned_alloc(size_t alignment, size_t size)
+{
+	void *ret;
+
+	if (posix_memalign(&ret, alignment, size))
+		return NULL;
+
+	return ret;
+}
diff --git a/test/helpers.h b/test/helpers.h
index 9e1cdf5ec05c..d0294eba63e4 100644
--- a/test/helpers.h
+++ b/test/helpers.h
@@ -4,36 +4,44 @@
  */
 #ifndef LIBURING_HELPERS_H
 #define LIBURING_HELPERS_H
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 #include "liburing.h"
 #include "../src/setup.h"
 #include <arpa/inet.h>
 #include <sys/time.h>
+#include <stdlib.h>
 
 enum t_setup_ret {
 	T_SETUP_OK	= 0,
 	T_SETUP_SKIP,
 };
 
 enum t_test_result {
 	T_EXIT_PASS   = 0,
 	T_EXIT_FAIL   = 1,
 	T_EXIT_SKIP   = 77,
 };
 
+/*
+ * Some Android versions lack aligned_alloc in stdlib.h.
+ * To avoid making large changes in tests, define a helper
+ * function that wraps posix_memalign as our own aligned_alloc.
+ */
+void *aligned_alloc(size_t alignment, size_t size);
+
 /*
  * Helper for binding socket to an ephemeral port.
  * The port number to be bound is returned in @addr->sin_port.
  */
 int t_bind_ephemeral_port(int fd, struct sockaddr_in *addr);
 
 
 /*
  * Helper for allocating memory in tests.
  */
 void *t_malloc(size_t size);
 
-- 
Ammar Faizi

Re: [PATCH liburing v1 0/3] Fix Compilation Error on Android and Some Cleanup

[Jens Axboe]

On Thu, 20 Feb 2025 21:34:19 +0700, Ammar Faizi wrote:
> Another day in the thrilling world of cross-platform compatibility...
> 
> Alviro discovered that some Android versions are missing `aligned_alloc()`
> in `<stdlib.h>`, leading to a compilation error on Termux 0.118.0:
> 
> ```
> cmd-discard.c:383:11: warning: call to undeclared library function \
> 'aligned_alloc' with type 'void *(unsigned long, unsigned long)'; ISO \
> C99 and later do not support implicit function declarations \
> [-Wimplicit-function-declaration]
> 
> [...]

Applied, thanks!

[1/3] liburing.h: Remove redundant double negation
      commit: 1d11475301931478bb35f2573e1741f5d9088132
[2/3] liburing.h: Explain the history of `io_uring_get_sqe()`
      commit: d1c100351ffb3483f5d3fc661b2d41d48062bec1
[3/3] Fix missing `aligned_alloc()` on some Android devices
      commit: 5c788d514b9ed6d1a3624150de8aa6db403c1c65

Best regards,
-- 
Jens Axboe