Fix build with _FILE_OFFSET_BITS=64

app/app.pro

@@ -271,7 +271,7 @@ libdrm {
 
     linux {
         message(Master hooks enabled)
-        SOURCES += masterhook.c
+        SOURCES += masterhook.c masterhook_internal.c
         LIBS += -ldl
     }
 }

app/masterhook.c

@@ -11,9 +11,12 @@
 
 #define _GNU_SOURCE
 
+// NOTE: This file MUST NOT include fcntl.h due to open() -> open64()
+// redirection that happens when _FILE_OFFSET_BITS=64!
+// See masterhook_internal.c for details.
+
 #include <SDL.h>
 #include <dlfcn.h>
-#include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
 #include <sys/stat.h>
@@ -21,16 +24,6 @@
 #include <xf86drm.h>
 #include <xf86drmMode.h>
 
-// __OPEN_NEEDS_MODE is a glibc-ism, so define it ourselves for other libc
-#ifndef __OPEN_NEEDS_MODE
-#ifdef __O_TMPFILE
-# define __OPEN_NEEDS_MODE(oflag) \
-  (((oflag) & O_CREAT) != 0 || ((oflag) & __O_TMPFILE) == __O_TMPFILE)
-#else
-# define __OPEN_NEEDS_MODE(oflag) (((oflag) & O_CREAT) != 0)
-#endif
-#endif
-
 // We require SDL 2.0.15+ to hook because it supports sharing
 // the DRM FD with our code. This avoids having multiple DRM FDs
 // in flight at the same time which would significantly complicate
@@ -96,12 +89,6 @@ int drmModeAtomicCommit(int fd, drmModeAtomicReqPtr req,
 // master on the Qt FD to allow the new FD to have master.
 int openHook(const char *funcname, const char *pathname, int flags, va_list va);
 
-// fcntl.h may define open to open64 which will cause us to define open64 twice.
-// Remove this redirection to allow our hooks to build properly with _FILE_OFFSET_BITS=64.
-#ifdef open
-#undef open
-#endif
-
 int open(const char *pathname, int flags, ...)
 {
     va_list va;
@@ -120,64 +107,6 @@ int open64(const char *pathname, int flags, ...)
     return fd;
 }
 
-int openHook(const char *funcname, const char *pathname, int flags, va_list va)
-{
-    int fd;
-    mode_t mode;
-
-    // Call the real thing to do the open operation
-    if (__OPEN_NEEDS_MODE(flags)) {
-        mode = va_arg(va, mode_t);
-        fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags, mode);
-    }
-    else {
-        mode = 0;
-        fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags);
-    }
-
-    // If the file was successfully opened and we have a DRM master FD,
-    // check if the FD we just opened is a DRM device.
-    if (fd >= 0 && g_QtDrmMasterFd != -1) {
-        if (strncmp(pathname, "/dev/dri/card", 13) == 0) {
-            // It's a DRM device, but is it _our_ DRM device?
-            struct stat64 fdstat;
-
-            fstat64(fd, &fdstat);
-            if (g_DrmMasterStat.st_dev == fdstat.st_dev &&
-                    g_DrmMasterStat.st_ino == fdstat.st_ino) {
-                // It is our device. Time to do the magic!
-
-                // This code assumes SDL only ever opens a single FD
-                // for a given DRM device.
-                SDL_assert(g_SdlDrmMasterFd == -1);
-
-                // Drop master on Qt's FD so we can pick it up for SDL.
-                if (drmDropMaster(g_QtDrmMasterFd) < 0) {
-                    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
-                                 "Failed to drop master on Qt DRM FD: %d",
-                                 errno);
-                    // Hope for the best
-                    return fd;
-                }
-
-                // We are not allowed to call drmSetMaster() without CAP_SYS_ADMIN,
-                // but since we just dropped the master, we can become master by
-                // simply creating a new FD. Let's do it.
-                close(fd);
-                if (__OPEN_NEEDS_MODE(flags)) {
-                    fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags, mode);
-                }
-                else {
-                    fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags);
-                }
-                g_SdlDrmMasterFd = fd;
-            }
-        }
-    }
-
-    return fd;
-}
-
 // Our close() hook handles restoring DRM master to the Qt FD
 // after SDL closes its DRM FD.
 int close(int fd)

app/masterhook_internal.c

@@ -0,0 +1,90 @@
+// This file contains the private implementation of the open() hook
+// which must be in a separate compilation unit due to fcntl.h doing
+// unwanted redirection of open() to open64().
+
+#define _GNU_SOURCE
+
+#include <SDL.h>
+#include <dlfcn.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/stat.h>
+
+#include <xf86drm.h>
+#include <xf86drmMode.h>
+
+// __OPEN_NEEDS_MODE is a glibc-ism, so define it ourselves for other libc
+#ifndef __OPEN_NEEDS_MODE
+#ifdef __O_TMPFILE
+# define __OPEN_NEEDS_MODE(oflag) \
+  (((oflag) & O_CREAT) != 0 || ((oflag) & __O_TMPFILE) == __O_TMPFILE)
+#else
+# define __OPEN_NEEDS_MODE(oflag) (((oflag) & O_CREAT) != 0)
+#endif
+#endif
+
+#if SDL_VERSION_ATLEAST(2, 0, 15)
+
+extern int g_QtDrmMasterFd;
+extern struct stat64 g_DrmMasterStat;
+extern int g_SdlDrmMasterFd;
+
+int openHook(const char *funcname, const char *pathname, int flags, va_list va)
+{
+    int fd;
+    mode_t mode;
+
+    // Call the real thing to do the open operation
+    if (__OPEN_NEEDS_MODE(flags)) {
+        mode = va_arg(va, mode_t);
+        fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags, mode);
+    }
+    else {
+        mode = 0;
+        fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags);
+    }
+
+    // If the file was successfully opened and we have a DRM master FD,
+    // check if the FD we just opened is a DRM device.
+    if (fd >= 0 && g_QtDrmMasterFd != -1) {
+        if (strncmp(pathname, "/dev/dri/card", 13) == 0) {
+            // It's a DRM device, but is it _our_ DRM device?
+            struct stat64 fdstat;
+
+            fstat64(fd, &fdstat);
+            if (g_DrmMasterStat.st_dev == fdstat.st_dev &&
+                    g_DrmMasterStat.st_ino == fdstat.st_ino) {
+                // It is our device. Time to do the magic!
+
+                // This code assumes SDL only ever opens a single FD
+                // for a given DRM device.
+                SDL_assert(g_SdlDrmMasterFd == -1);
+
+                // Drop master on Qt's FD so we can pick it up for SDL.
+                if (drmDropMaster(g_QtDrmMasterFd) < 0) {
+                    SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
+                                 "Failed to drop master on Qt DRM FD: %d",
+                                 errno);
+                    // Hope for the best
+                    return fd;
+                }
+
+                // We are not allowed to call drmSetMaster() without CAP_SYS_ADMIN,
+                // but since we just dropped the master, we can become master by
+                // simply creating a new FD. Let's do it.
+                close(fd);
+                if (__OPEN_NEEDS_MODE(flags)) {
+                    fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags, mode);
+                }
+                else {
+                    fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags);
+                }
+                g_SdlDrmMasterFd = fd;
+            }
+        }
+    }
+
+    return fd;
+}
+#endif