diff --git a/api/boinc_api.C b/api/boinc_api.C
index b69c5946a5..59c6aa0d9b 100644
--- a/api/boinc_api.C
+++ b/api/boinc_api.C
@@ -169,9 +169,7 @@ static int setup_shared_mem() {
     }
 #else
 #ifdef USE_FILE_MAPPED_SHMEM
-    if (create_shmem(
-            MMAPPED_FILE_NAME, sizeof(SHARED_MEM), (void**)&app_client_shm->shm
-        )) {
+    if (attach_shmem( MMAPPED_FILE_NAME, (void**)&app_client_shm->shm)) {
         delete app_client_shm;
         app_client_shm = NULL;
     }
diff --git a/lib/shmem.C b/lib/shmem.C
index a696179149..235b7dd655 100755
--- a/lib/shmem.C
+++ b/lib/shmem.C
@@ -181,23 +181,16 @@ int create_shmem(char *path, size_t size, void** pp) {
     // and it's not a significant security issue.
     //
     fd = open(path, O_RDWR | O_CREAT, 0666);
-    if (fd < 0)
-        return ERR_SHMGET;
+    if (fd < 0) return ERR_SHMGET;
 
     retval = fstat(fd, &sbuf);
-    if (retval == 0) {
-        if (sbuf.st_size < size) {
-            // The following 2 lines extend the file and clear its new 
-            // area to all zeros because they write beyond the old EOF. 
-            // See the lseek man page for details.
-            lseek(fd, size-1, SEEK_SET);
-            write(fd, "\0", 1);
-        }
-    }
-    
-    if (retval) {
-        perror("fcntl returned ");
-       return ERR_SHMGET;
+    if (retval) return ERR_SHMGET;
+    if (sbuf.st_size < size) {
+        // The following 2 lines extend the file and clear its new 
+        // area to all zeros because they write beyond the old EOF. 
+        // See the lseek man page for details.
+        lseek(fd, size-1, SEEK_SET);
+        write(fd, "\0", 1);
     }
 
     // mmap willl return NULL if size is 0
@@ -206,9 +199,11 @@ int create_shmem(char *path, size_t size, void** pp) {
     // Now close the file. The kernel doesnŐt use our file descriptor.
     close(fd);
 
-    if (*pp == MAP_FAILED)
+    if (*pp == MAP_FAILED) {
+        *pp = 0;
         return ERR_SHMGET;
-
+    }
+    
     return 0;
 }
 
@@ -216,6 +211,30 @@ int destroy_shmem(key_t key){
     return 0;
 }
 
+int attach_shmem(char *path, void** pp) {
+    int fd, retval;
+    struct stat sbuf;
+    
+    fd = open(path, O_RDWR);
+    if (fd < 0) return ERR_SHMGET;
+
+    retval = fstat(fd, &sbuf);
+    if (retval) return ERR_SHMGET;
+
+    *pp = mmap(NULL, sbuf.st_size, PROT_READ | PROT_WRITE, MAP_FILE | MAP_SHARED, fd, 0);
+    
+    // Now close the file. The kernel doesnŐt use our file descriptor.
+    close(fd);
+
+    if (*pp == MAP_FAILED) {
+        *pp = 0;
+        return ERR_SHMGET;
+    }
+    
+    return 0;
+}
+
+
 int detach_shmem(void* p, size_t size) {
     return munmap(p, size);
 }
diff --git a/lib/shmem.h b/lib/shmem.h
index 6a21ece501..9dfc9778da 100755
--- a/lib/shmem.h
+++ b/lib/shmem.h
@@ -52,6 +52,10 @@ int detach_shmem(HANDLE hSharedMem, void* p);
 //
 extern int create_shmem(char *path, size_t size, void** pp);
 
+// attach to a shared-memory segment
+//
+int attach_shmem(char *path, void** pp);
+
 // detach from a shared-mem segment
 //
 extern int detach_shmem(void* p, size_t size);
diff --git a/mac_build/boinc.xcodeproj/project.pbxproj b/mac_build/boinc.xcodeproj/project.pbxproj
index 6cb63ce053..346332d32b 100755
--- a/mac_build/boinc.xcodeproj/project.pbxproj
+++ b/mac_build/boinc.xcodeproj/project.pbxproj
@@ -3622,8 +3622,7 @@
 				OTHER_CFLAGS = (
 					"-DMAC_OS_X_VERSION_MAX_ALLOWED=1040",
 					"-D_THREAD_SAFE",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -3658,8 +3657,7 @@
 				OTHER_CFLAGS = (
 					"-D_THREAD_SAFE",
 					"-DNDEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -3764,10 +3762,7 @@
 				LIBRARY_STYLE = STATIC;
 				MACOSX_DEPLOYMENT_TARGET = "";
 				OPTIMIZATION_CFLAGS = "-O0";
-				OTHER_CFLAGS = (
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
-				);
+				OTHER_CFLAGS = "-DUSE_FILE_MAPPED_SHMEM";
 				OTHER_CPLUSPLUSFLAGS = "$(OTHER_CFLAGS)";
 				OTHER_LDFLAGS = "";
 				OTHER_REZFLAGS = "";
@@ -3792,10 +3787,7 @@
 				INSTALL_PATH = /usr/local/lib;
 				LIBRARY_STYLE = STATIC;
 				MACOSX_DEPLOYMENT_TARGET = 10.4;
-				OTHER_CFLAGS = (
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
-				);
+				OTHER_CFLAGS = "-DUSE_FILE_MAPPED_SHMEM";
 				OTHER_CFLAGS_i386 = "-DMAC_OS_X_VERSION_MAX_ALLOWED=1040 -D_THREAD_SAFE -include ../clientgui/mac/config.h";
 				OTHER_CFLAGS_ppc = "-DMAC_OS_X_VERSION_MAX_ALLOWED=1030 -D_THREAD_SAFE -include ../clientgui/mac/config.h";
 				OTHER_CPLUSPLUSFLAGS = "$(OTHER_CFLAGS)";
@@ -3958,8 +3950,7 @@
 					"-DMAC_OS_X_VERSION_MAX_ALLOWED=1040",
 					"-D_THREAD_SAFE",
 					"-D_DEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -4008,8 +3999,7 @@
 				OTHER_CFLAGS = (
 					"-D_THREAD_SAFE",
 					"-DNDEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -4797,8 +4787,7 @@
 				OTHER_CFLAGS = (
 					"-D_THREAD_SAFE",
 					"-DNDEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -4865,10 +4854,7 @@
 				INSTALL_PATH = /usr/local/lib;
 				LIBRARY_STYLE = STATIC;
 				MACOSX_DEPLOYMENT_TARGET = 10.4;
-				OTHER_CFLAGS = (
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
-				);
+				OTHER_CFLAGS = "-DUSE_FILE_MAPPED_SHMEM";
 				OTHER_CFLAGS_i386 = "-DMAC_OS_X_VERSION_MAX_ALLOWED=1040 -D_THREAD_SAFE -include ../clientgui/mac/config.h";
 				OTHER_CFLAGS_ppc = "-DMAC_OS_X_VERSION_MAX_ALLOWED=1030 -D_THREAD_SAFE -include ../clientgui/mac/config.h";
 				OTHER_CPLUSPLUSFLAGS = "$(OTHER_CFLAGS)";
@@ -4969,8 +4955,7 @@
 					"-D_THREAD_SAFE",
 					"-DSANDBOX",
 					"-DNDEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -5183,8 +5168,7 @@
 				OTHER_CFLAGS = (
 					"-DMAC_OS_X_VERSION_MAX_ALLOWED=1040",
 					"-D_THREAD_SAFE",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -5219,8 +5203,7 @@
 				OTHER_CFLAGS = (
 					"-DMAC_OS_X_VERSION_MAX_ALLOWED=1030",
 					"-D_THREAD_SAFE",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-DNDEBUG",
 					"-include",
 					../clientgui/mac/config.h,
@@ -5323,10 +5306,7 @@
 				LIBRARY_STYLE = STATIC;
 				MACOSX_DEPLOYMENT_TARGET = "";
 				OPTIMIZATION_CFLAGS = "-O0";
-				OTHER_CFLAGS = (
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
-				);
+				OTHER_CFLAGS = "-DUSE_FILE_MAPPED_SHMEM";
 				OTHER_CPLUSPLUSFLAGS = "$(OTHER_CFLAGS)";
 				OTHER_LDFLAGS = "";
 				OTHER_REZFLAGS = "";
@@ -5351,10 +5331,7 @@
 				INSTALL_PATH = /usr/local/lib;
 				LIBRARY_STYLE = STATIC;
 				MACOSX_DEPLOYMENT_TARGET = 10.3;
-				OTHER_CFLAGS = (
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
-				);
+				OTHER_CFLAGS = "-DUSE_FILE_MAPPED_SHMEM";
 				OTHER_CPLUSPLUSFLAGS = "$(OTHER_CFLAGS)";
 				OTHER_LDFLAGS = "";
 				OTHER_REZFLAGS = "";
@@ -5515,8 +5492,7 @@
 					"-D_THREAD_SAFE",
 					"-DSANDBOX",
 					"-D_DEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -5564,8 +5540,7 @@
 					"-D_THREAD_SAFE",
 					"-DSANDBOX",
 					"-DNDEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -5929,8 +5904,7 @@
 				OTHER_CFLAGS = (
 					"-DMAC_OS_X_VERSION_MAX_ALLOWED=1040",
 					"-D_THREAD_SAFE",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-DNDEBUG",
 					"-include",
 					../clientgui/mac/config.h,
@@ -5995,10 +5969,7 @@
 				INSTALL_PATH = /usr/local/lib;
 				LIBRARY_STYLE = STATIC;
 				MACOSX_DEPLOYMENT_TARGET = 10.4;
-				OTHER_CFLAGS = (
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
-				);
+				OTHER_CFLAGS = "-DUSE_FILE_MAPPED_SHMEM";
 				OTHER_CPLUSPLUSFLAGS = "$(OTHER_CFLAGS)";
 				OTHER_LDFLAGS = "";
 				OTHER_REZFLAGS = "";
@@ -6093,8 +6064,7 @@
 					"-D_THREAD_SAFE",
 					"-DSANDBOX",
 					"-DNDEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -6294,8 +6264,7 @@
 				OTHER_CFLAGS = (
 					"-DMAC_OS_X_VERSION_MAX_ALLOWED=1040",
 					"-D_THREAD_SAFE",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -6330,8 +6299,7 @@
 				OTHER_CFLAGS = (
 					"-DMAC_OS_X_VERSION_MAX_ALLOWED=1040",
 					"-D_THREAD_SAFE",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -6364,8 +6332,7 @@
 				OTHER_CFLAGS = (
 					"-DMAC_OS_X_VERSION_MAX_ALLOWED=1030",
 					"-D_THREAD_SAFE",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-DNDEBUG",
 					"-include",
 					../clientgui/mac/config.h,
@@ -6399,8 +6366,7 @@
 				OTHER_CFLAGS = (
 					"-DMAC_OS_X_VERSION_MAX_ALLOWED=1040",
 					"-D_THREAD_SAFE",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-DNDEBUG",
 					"-include",
 					../clientgui/mac/config.h,
@@ -6434,8 +6400,7 @@
 				OTHER_CFLAGS = (
 					"-D_THREAD_SAFE",
 					"-DNDEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);
@@ -6470,8 +6435,7 @@
 				OTHER_CFLAGS = (
 					"-D_THREAD_SAFE",
 					"-DNDEBUG",
-					"-D",
-					USE_FILE_MAPPED_SHMEM,
+					"-DUSE_FILE_MAPPED_SHMEM",
 					"-include",
 					../clientgui/mac/config.h,
 				);