util: Share qemu_try_memalign() implementation between POSIX and Windows

The qemu_try_memalign() functions for POSIX and Windows used to be
significantly different, but these days they are identical except for
the actual allocation function called, and the POSIX version already
has to have ifdeffery for different allocation functions.

Move to a single implementation in memalign.c, which uses the Windows
_aligned_malloc if we detect that function in meson.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220226180723.1706285-7-peter.maydell@linaro.org
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

meson.build

@@ -1622,6 +1622,7 @@ config_host_data.set('CONFIG_POSIX_FALLOCATE', cc.has_function('posix_fallocate'
 # Note that we need to specify prefix: here to avoid incorrectly
 # thinking that Windows has posix_memalign()
 config_host_data.set('CONFIG_POSIX_MEMALIGN', cc.has_function('posix_memalign', prefix: '#include <stdlib.h>'))
+config_host_data.set('CONFIG_ALIGNED_MALLOC', cc.has_function('_aligned_malloc'))
 config_host_data.set('CONFIG_PPOLL', cc.has_function('ppoll'))
 config_host_data.set('CONFIG_PREADV', cc.has_function('preadv', prefix: '#include <sys/uio.h>'))
 config_host_data.set('CONFIG_SEM_TIMEDWAIT', cc.has_function('sem_timedwait', dependencies: threads))

util/memalign.c

@@ -25,6 +25,45 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/host-utils.h"
+#include "trace.h"
+
+void *qemu_try_memalign(size_t alignment, size_t size)
+{
+    void *ptr;
+
+    if (alignment < sizeof(void*)) {
+        alignment = sizeof(void*);
+    } else {
+        g_assert(is_power_of_2(alignment));
+    }
+
+    /*
+     * Handling of 0 allocations varies among the different
+     * platform APIs (for instance _aligned_malloc() will
+     * fail) -- ensure that we always return a valid non-NULL
+     * pointer that can be freed by qemu_vfree().
+     */
+    if (size == 0) {
+        size++;
+    }
+#if defined(CONFIG_POSIX_MEMALIGN)
+    int ret;
+    ret = posix_memalign(&ptr, alignment, size);
+    if (ret != 0) {
+        errno = ret;
+        ptr = NULL;
+    }
+#elif defined(CONFIG_ALIGNED_MALLOC)
+    ptr = _aligned_malloc(size, alignment);
+#elif defined(CONFIG_BSD)
+    ptr = valloc(size);
+#else
+    ptr = memalign(alignment, size);
+#endif
+    trace_qemu_memalign(alignment, size, ptr);
+    return ptr;
+}
 
 void *qemu_memalign(size_t alignment, size_t size)
 {

util/oslib-posix.c

@@ -199,35 +199,6 @@ fail_close:
     return false;
 }
 
-void *qemu_try_memalign(size_t alignment, size_t size)
-{
-    void *ptr;
-
-    if (alignment < sizeof(void*)) {
-        alignment = sizeof(void*);
-    } else {
-        g_assert(is_power_of_2(alignment));
-    }
-
-    if (size == 0) {
-        size++;
-    }
-#if defined(CONFIG_POSIX_MEMALIGN)
-    int ret;
-    ret = posix_memalign(&ptr, alignment, size);
-    if (ret != 0) {
-        errno = ret;
-        ptr = NULL;
-    }
-#elif defined(CONFIG_BSD)
-    ptr = valloc(size);
-#else
-    ptr = memalign(alignment, size);
-#endif
-    trace_qemu_memalign(alignment, size, ptr);
-    return ptr;
-}
-
 /* alloc shared memory pages */
 void *qemu_anon_ram_alloc(size_t size, uint64_t *alignment, bool shared,
                           bool noreserve)

util/oslib-win32.c

@@ -44,23 +44,6 @@
 /* this must come after including "trace.h" */
 #include <shlobj.h>
 
-void *qemu_try_memalign(size_t alignment, size_t size)
-{
-    void *ptr;
-
-    if (alignment < sizeof(void *)) {
-        alignment = sizeof(void *);
-    } else {
-        g_assert(is_power_of_2(alignment));
-    }
-    if (size == 0) {
-        size++;
-    }
-    ptr = _aligned_malloc(size, alignment);
-    trace_qemu_memalign(alignment, size, ptr);
-    return ptr;
-}
-
 static int get_allocation_granularity(void)
 {
     SYSTEM_INFO system_info;