[PATCH libaio v3 3/9] Use new symver function attribute to support LTO builds

From: Guillem Jover <[email protected]>

The LTO support cannot work properly when there are versioned symbols
via asm statements, as those are not seen by the compiler. Use the new
function attributes if supported instead of the asm statements.

We need to move the SYMVER calls after the function definitions
otherwise it will reference symbols not yet seen.

Even though this library will not benefit much, if at all, from LTO,
most major distributions have switched their toolchains to enable LTO
by default, which means the library does not build out of the box in
those systems.

Fixes: https://codeberg.org/jmoyer/libaio/issues/10
Signed-off-by: Guillem Jover <[email protected]>
---
 src/compat-0_1.c |  7 +++----
 src/syscall.h    | 13 +++++++++++++
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/compat-0_1.c b/src/compat-0_1.c
index 722e107..ac40fcc 100644
--- a/src/compat-0_1.c
+++ b/src/compat-0_1.c
@@ -28,7 +28,6 @@
 
 
 /* ABI change.  Provide partial compatibility on this one for now. */
-SYMVER(compat0_1_io_cancel, io_cancel, 0.1);
 int compat0_1_io_cancel(io_context_t ctx, struct iocb *iocb)
 {
 	struct io_event event;
@@ -36,8 +35,8 @@ int compat0_1_io_cancel(io_context_t ctx, struct iocb *iocb)
 	/* FIXME: the old ABI would return the event on the completion queue */
 	return io_cancel(ctx, iocb, &event);
 }
+SYMVER(compat0_1_io_cancel, io_cancel, 0.1);
 
-SYMVER(compat0_1_io_queue_wait, io_queue_wait, 0.1);
 int compat0_1_io_queue_wait(io_context_t ctx, struct timespec *when)
 {
 	struct timespec timeout;
@@ -45,10 +44,10 @@ int compat0_1_io_queue_wait(io_context_t ctx, struct timespec *when)
 		timeout = *when;
 	return io_getevents(ctx, 0, 0, NULL, when ? &timeout : NULL);
 }
+SYMVER(compat0_1_io_queue_wait, io_queue_wait, 0.1);
 
 
 /* ABI change.  Provide backwards compatibility for this one. */
-SYMVER(compat0_1_io_getevents, io_getevents, 0.1);
 int compat0_1_io_getevents(io_context_t ctx, long nr,
 		       struct io_event *events,
 		       const struct timespec *const_timeout)
@@ -59,4 +58,4 @@ int compat0_1_io_getevents(io_context_t ctx, long nr,
 	return io_getevents(ctx, 1, nr, events,
 			const_timeout ? &timeout : NULL);
 }
-
+SYMVER(compat0_1_io_getevents, io_getevents, 0.1);
diff --git a/src/syscall.h b/src/syscall.h
index f7ce979..59e0bb3 100644
--- a/src/syscall.h
+++ b/src/syscall.h
@@ -2,14 +2,27 @@
 #include <unistd.h>
 #include <errno.h>
 
+#ifndef __has_attribute
+#define __has_attribute(x) 0
+#endif
+
 #define _SYMSTR(str)	#str
 #define SYMSTR(str)	_SYMSTR(str)
 
+#if __has_attribute(__symver__)
+#define SYMVER(compat_sym, orig_sym, ver_sym)	\
+	extern __typeof(compat_sym) compat_sym \
+	  __attribute__((__symver__(SYMSTR(orig_sym) "@LIBAIO_" SYMSTR(ver_sym))))
+#define DEFSYMVER(compat_sym, orig_sym, ver_sym)	\
+	extern __typeof(compat_sym) compat_sym \
+	  __attribute__((__symver__(SYMSTR(orig_sym) "@@LIBAIO_" SYMSTR(ver_sym))))
+#else
 #define SYMVER(compat_sym, orig_sym, ver_sym)	\
 	__asm__(".symver " SYMSTR(compat_sym) "," SYMSTR(orig_sym) "@LIBAIO_" SYMSTR(ver_sym))
 
 #define DEFSYMVER(compat_sym, orig_sym, ver_sym)	\
 	__asm__(".symver " SYMSTR(compat_sym) "," SYMSTR(orig_sym) "@@LIBAIO_" SYMSTR(ver_sym))
+#endif
 
 #if defined(__i386__)
 #include "syscall-i386.h"
-- 
2.53.0


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