util/osdep: Avoid madvise proto on modern Solaris

On older Solaris releases (before Solaris 11), we didn't get a
prototype for madvise, and so util/osdep.c provides its own prototype.
Some time between the public Solaris 11.4 release and Solaris 11.4.42
CBE, we started getting an madvise prototype that looks like this:

    extern int madvise(void *, size_t, int);

which conflicts with the prototype in util/osdeps.c. Instead of always
declaring this prototype, check if we're missing the madvise()
prototype, and only declare it ourselves if the prototype is missing.
Move the prototype to include/qemu/osdep.h, the normal place to handle
platform-specific header quirks.

The 'missing_madvise_proto' meson check contains an obviously wrong
prototype for madvise. So if that code compiles and links, we must be
missing the actual prototype for madvise.

Signed-off-by: Andrew Deason <adeason@sinenomine.net>
Message-id: 20220316035227.3702-2-adeason@sinenomine.net
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 29 insertions, 5 deletions

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 322103a..f2274b2 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -400,6 +400,14 @@ void qemu_anon_ram_free(void *ptr, size_t size);
 #define SIGIO SIGPOLL
 #endif
 
+#ifdef HAVE_MADVISE_WITHOUT_PROTOTYPE
+/*
+ * See MySQL bug #7156 (http://bugs.mysql.com/bug.php?id=7156) for discussion
+ * about Solaris missing the madvise() prototype.
+ */
+extern int madvise(char *, size_t, int);
+#endif
+
 #if defined(CONFIG_LINUX)
 #ifndef BUS_MCEERR_AR
 #define BUS_MCEERR_AR 4
diff --git a/meson.build b/meson.build
index bae62ef..282e7c4 100644
--- a/meson.build
+++ b/meson.build
@@ -1715,11 +1715,30 @@ config_host_data.set('CONFIG_FDATASYNC', cc.links(gnu_source_prefix + '''
   #error Not supported
   #endif
   }'''))
-config_host_data.set('CONFIG_MADVISE', cc.links(gnu_source_prefix + '''
+
+has_madvise = cc.links(gnu_source_prefix + '''
   #include <sys/types.h>
   #include <sys/mman.h>
   #include <stddef.h>
-  int main(void) { return madvise(NULL, 0, MADV_DONTNEED); }'''))
+  int main(void) { return madvise(NULL, 0, MADV_DONTNEED); }''')
+missing_madvise_proto = false
+if has_madvise
+  # Some platforms (illumos and Solaris before Solaris 11) provide madvise()
+  # but forget to prototype it. In this case, has_madvise will be true (the
+  # test program links despite a compile warning). To detect the
+  # missing-prototype case, we try again with a definitely-bogus prototype.
+  # This will only compile if the system headers don't provide the prototype;
+  # otherwise the conflicting prototypes will cause a compiler error.
+  missing_madvise_proto = cc.links(gnu_source_prefix + '''
+    #include <sys/types.h>
+    #include <sys/mman.h>
+    #include <stddef.h>
+    extern int madvise(int);
+    int main(void) { return madvise(0); }''')
+endif
+config_host_data.set('CONFIG_MADVISE', has_madvise)
+config_host_data.set('HAVE_MADVISE_WITHOUT_PROTOTYPE', missing_madvise_proto)
+
 config_host_data.set('CONFIG_MEMFD', cc.links(gnu_source_prefix + '''
   #include <sys/mman.h>
   int main(void) { return memfd_create("foo", MFD_ALLOW_SEALING); }'''))
diff --git a/util/osdep.c b/util/osdep.c
index 7c4deda..1825399 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -28,9 +28,6 @@
 
 #ifdef CONFIG_SOLARIS
 #include <sys/statvfs.h>
-/* See MySQL bug #7156 (http://bugs.mysql.com/bug.php?id=7156) for
-   discussion about Solaris header problems */
-extern int madvise(char *, size_t, int);
 #endif
 
 #include "qemu-common.h"