Instead of assuming that all CONFIG_BSD have valloc() and anything
else is memalign(), explicitly check for those functions in
meson.build and use the "is the function present" define.  Tests for
specific functionality are better than which-OS checks; this also
lets us give a helpful error message if somehow there's no usable
function present.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20220226180723.1706285-8-peter.maydell@linaro.org
---
 meson.build     | 2 ++
 util/memalign.c | 6 ++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/meson.build b/meson.build
index bc0ac931e1a..774d0248a62 100644
--- a/meson.build
+++ b/meson.build
@@ -1623,6 +1623,8 @@ config_host_data.set('CONFIG_POSIX_FALLOCATE', cc.has_function('posix_fallocate'
 # 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_VALLOC', cc.has_function('valloc'))
+config_host_data.set('CONFIG_MEMALIGN', cc.has_function('memalign'))
 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))
diff --git a/util/memalign.c b/util/memalign.c
index 22b405700e3..083aaae619c 100644
--- a/util/memalign.c
+++ b/util/memalign.c
@@ -56,10 +56,12 @@ void *qemu_try_memalign(size_t alignment, size_t size)
     }
 #elif defined(CONFIG_ALIGNED_MALLOC)
     ptr = _aligned_malloc(size, alignment);
-#elif defined(CONFIG_BSD)
+#elif defined(CONFIG_VALLOC)
     ptr = valloc(size);
-#else
+#elif defined(CONFIG_MEMALIGN)
     ptr = memalign(alignment, size);
+#else
+    #error No function to allocate aligned memory available
 #endif
     trace_qemu_memalign(alignment, size, ptr);
     return ptr;
-- 
2.25.1