From d04ccb8ebe12c52d9c4fb560aadd48900b9e9dfb Mon Sep 17 00:00:00 2001
From: Alexandre Julliard <julliard@winehq.org>
Date: Tue, 4 Mar 2003 22:18:43 +0000
Subject: [PATCH] Use SIGUSR1 instead of SIGSTOP to suspend threads.

---
 dlls/ntdll/signal_i386.c       | 46 +++++++++++++++++++
 dlls/ntdll/signal_powerpc.c    | 15 +++++++
 dlls/ntdll/signal_sparc.c      | 15 +++++++
 include/wine/server_protocol.h |  2 +-
 scheduler/client.c             |  2 +
 scheduler/process.c            | 13 +++---
 server/context_i386.c          |  6 +--
 server/context_powerpc.c       |  6 +--
 server/context_sparc.c         |  6 +--
 server/process.c               | 10 ++---
 server/ptrace.c                | 81 ++++++++++++++--------------------
 server/thread.c                | 24 +++++-----
 server/thread.h                |  7 +--
 server/trace.c                 | 11 +++++
 14 files changed, 158 insertions(+), 86 deletions(-)

diff --git a/dlls/ntdll/signal_i386.c b/dlls/ntdll/signal_i386.c
index 668e5e242a2..fd80bd2f1fb 100644
--- a/dlls/ntdll/signal_i386.c
+++ b/dlls/ntdll/signal_i386.c
@@ -654,6 +654,36 @@ static void restore_context( const CONTEXT *context, SIGCONTEXT *sigcontext )
 }
 
 
+/***********************************************************************
+ *           init_handler
+ *
+ * Handler initialization when the full context is not needed.
+ */
+static void init_handler( const SIGCONTEXT *sigcontext )
+{
+    /* restore a proper %fs for the fault handler */
+    if (!IS_SELECTOR_SYSTEM(CS_sig(sigcontext)) ||
+        !IS_SELECTOR_SYSTEM(SS_sig(sigcontext)))  /* 16-bit mode */
+    {
+        wine_set_fs( SYSLEVEL_Win16CurrentTeb );
+    }
+#ifdef __HAVE_VM86
+    else if ((void *)EIP_sig(sigcontext) == vm86_return)  /* vm86 mode */
+    {
+        /* fetch the saved %fs on the stack */
+        wine_set_fs( *(unsigned int *)ESP_sig(sigcontext) );
+    }
+#endif  /* __HAVE_VM86 */
+#ifdef FS_sig
+    else  /* 32-bit mode, get %fs at time of the fault */
+    {
+        wine_set_fs( FS_sig(sigcontext) );
+    }
+#endif  /* FS_sig */
+    wine_set_gs( NtCurrentTeb()->gs_sel );
+}
+
+
 /***********************************************************************
  *           save_fpu
  *
@@ -1037,6 +1067,7 @@ static HANDLER_DEF(fpe_handler)
  */
 static HANDLER_DEF(int_handler)
 {
+    init_handler( HANDLER_CONTEXT );
     if (!dispatch_signal(SIGINT))
     {
         EXCEPTION_RECORD rec;
@@ -1074,6 +1105,19 @@ static HANDLER_DEF(abrt_handler)
 }
 
 
+/**********************************************************************
+ *		usr1_handler
+ *
+ * Handler for SIGUSR1, used to signal a thread that it got suspended.
+ */
+static HANDLER_DEF(usr1_handler)
+{
+    init_handler( HANDLER_CONTEXT );
+    /* wait with 0 timeout, will only return once the thread is no longer suspended */
+    WaitForMultipleObjectsEx( 0, NULL, FALSE, 0, FALSE );
+}
+
+
 /***********************************************************************
  *           set_handler
  *
@@ -1160,6 +1204,7 @@ BOOL SIGNAL_Init(void)
     if (set_handler( SIGSEGV, have_sigaltstack, (void (*)())segv_handler ) == -1) goto error;
     if (set_handler( SIGILL,  have_sigaltstack, (void (*)())segv_handler ) == -1) goto error;
     if (set_handler( SIGABRT, have_sigaltstack, (void (*)())abrt_handler ) == -1) goto error;
+    if (set_handler( SIGUSR1, have_sigaltstack, (void (*)())usr1_handler ) == -1) goto error;
 #ifdef SIGBUS
     if (set_handler( SIGBUS,  have_sigaltstack, (void (*)())segv_handler ) == -1) goto error;
 #endif
@@ -1192,6 +1237,7 @@ void SIGNAL_Reset(void)
     sigaddset( &block_set, SIGALRM );
     sigaddset( &block_set, SIGIO );
     sigaddset( &block_set, SIGHUP );
+    sigaddset( &block_set, SIGUSR1 );
     sigaddset( &block_set, SIGUSR2 );
     sigprocmask( SIG_BLOCK, &block_set, NULL );
 
diff --git a/dlls/ntdll/signal_powerpc.c b/dlls/ntdll/signal_powerpc.c
index 6259d12c9ec..b3d279ae6a7 100644
--- a/dlls/ntdll/signal_powerpc.c
+++ b/dlls/ntdll/signal_powerpc.c
@@ -381,6 +381,7 @@ static HANDLER_DEF(int_handler)
     }
 }
 
+
 /**********************************************************************
  *		abrt_handler
  *
@@ -402,6 +403,18 @@ static HANDLER_DEF(abrt_handler)
 }
 
 
+/**********************************************************************
+ *		usr1_handler
+ *
+ * Handler for SIGUSR1, used to signal a thread that it got suspended.
+ */
+static HANDLER_DEF(usr1_handler)
+{
+    /* wait with 0 timeout, will only return once the thread is no longer suspended */
+    WaitForMultipleObjectsEx( 0, NULL, FALSE, 0, FALSE );
+}
+
+
 /***********************************************************************
  *           set_handler
  *
@@ -461,6 +474,7 @@ BOOL SIGNAL_Init(void)
     if (set_handler( SIGSEGV, have_sigaltstack, (void (*)())segv_handler ) == -1) goto error;
     if (set_handler( SIGILL,  have_sigaltstack, (void (*)())segv_handler ) == -1) goto error;
     if (set_handler( SIGABRT, have_sigaltstack, (void (*)())abrt_handler ) == -1) goto error;
+    if (set_handler( SIGUSR1, have_sigaltstack, (void (*)())usr1_handler ) == -1) goto error;
 #ifdef SIGBUS
     if (set_handler( SIGBUS,  have_sigaltstack, (void (*)())segv_handler ) == -1) goto error;
 #endif
@@ -488,6 +502,7 @@ void SIGNAL_Reset(void)
     sigaddset( &block_set, SIGALRM );
     sigaddset( &block_set, SIGIO );
     sigaddset( &block_set, SIGHUP );
+    sigaddset( &block_set, SIGUSR1 );
     sigaddset( &block_set, SIGUSR2 );
     sigprocmask( SIG_BLOCK, &block_set, NULL );
 
diff --git a/dlls/ntdll/signal_sparc.c b/dlls/ntdll/signal_sparc.c
index 7ac34c8ba36..1ba4038681c 100644
--- a/dlls/ntdll/signal_sparc.c
+++ b/dlls/ntdll/signal_sparc.c
@@ -367,6 +367,19 @@ static HANDLER_DEF(abrt_handler)
     restore_context( &context, HANDLER_CONTEXT );
 }
 
+
+/**********************************************************************
+ *		usr1_handler
+ *
+ * Handler for SIGUSR1, used to signal a thread that it got suspended.
+ */
+static HANDLER_DEF(usr1_handler)
+{
+    /* wait with 0 timeout, will only return once the thread is no longer suspended */
+    WaitForMultipleObjectsEx( 0, NULL, FALSE, 0, FALSE );
+}
+
+
 /***********************************************************************
  *           set_handler
  *
@@ -422,6 +435,7 @@ BOOL SIGNAL_Init(void)
     if (set_handler( SIGBUS,  (void (*)())bus_handler  ) == -1) goto error;
     if (set_handler( SIGTRAP, (void (*)())trap_handler ) == -1) goto error;
     if (set_handler( SIGABRT, (void (*)())abrt_handler ) == -1) goto error;
+    if (set_handler( SIGUSR1, (void (*)())usr1_handler ) == -1) goto error;
    return TRUE;
 
  error:
@@ -442,6 +456,7 @@ void SIGNAL_Reset(void)
     sigaddset( &block_set, SIGALRM );
     sigaddset( &block_set, SIGIO );
     sigaddset( &block_set, SIGHUP );
+    sigaddset( &block_set, SIGUSR1 );
     sigaddset( &block_set, SIGUSR2 );
     sigprocmask( SIG_BLOCK, &block_set, NULL );
 
diff --git a/include/wine/server_protocol.h b/include/wine/server_protocol.h
index c5b5e4c7be9..5555f062f0b 100644
--- a/include/wine/server_protocol.h
+++ b/include/wine/server_protocol.h
@@ -3551,6 +3551,6 @@ union generic_reply
     struct get_next_hook_reply get_next_hook_reply;
 };
 
-#define SERVER_PROTOCOL_VERSION 98
+#define SERVER_PROTOCOL_VERSION 99
 
 #endif /* __WINE_WINE_SERVER_PROTOCOL_H */
diff --git a/scheduler/client.c b/scheduler/client.c
index ef6db594a77..466fef74100 100644
--- a/scheduler/client.c
+++ b/scheduler/client.c
@@ -653,6 +653,8 @@ void CLIENT_InitServer(void)
     sigaddset( &block_set, SIGIO );
     sigaddset( &block_set, SIGINT );
     sigaddset( &block_set, SIGHUP );
+    sigaddset( &block_set, SIGUSR1 );
+    sigaddset( &block_set, SIGUSR2 );
 
     /* receive the first thread request fd on the main socket */
     NtCurrentTeb()->request_fd = receive_fd( &dummy_handle );
diff --git a/scheduler/process.c b/scheduler/process.c
index 2d1eb95e523..ea9a3056bf4 100644
--- a/scheduler/process.c
+++ b/scheduler/process.c
@@ -508,6 +508,14 @@ static void start_process(void)
     console_app = (nt->OptionalHeader.Subsystem == IMAGE_SUBSYSTEM_WINDOWS_CUI);
     if (console_app) current_process.flags |= PDB32_CONSOLE_PROC;
 
+    /* Install signal handlers; this cannot be done before, since we cannot
+     * send exceptions to the debugger before the create process event that
+     * is sent by REQ_INIT_PROCESS_DONE.
+     * We do need the handlers in place by the time the request is over, so
+     * we set them up here. If we segfault between here and the server call
+     * something is very wrong... */
+    if (!SIGNAL_Init()) goto error;
+
     /* Signal the parent process to continue */
     SERVER_START_REQ( init_process_done )
     {
@@ -524,11 +532,6 @@ static void start_process(void)
     }
     SERVER_END_REQ;
 
-    /* Install signal handlers; this cannot be done before, since we cannot
-     * send exceptions to the debugger before the create process event that
-     * is sent by REQ_INIT_PROCESS_DONE */
-    if (!SIGNAL_Init()) goto error;
-
     /* create the main modref and load dependencies */
     if (!(wm = PE_CreateModule( current_process.module, main_exe_name, 0, 0, FALSE )))
         goto error;
diff --git a/server/context_i386.c b/server/context_i386.c
index b7a7bb03751..75028cf1376 100644
--- a/server/context_i386.c
+++ b/server/context_i386.c
@@ -534,7 +534,7 @@ void *get_thread_ip( struct thread *thread )
     if (suspend_for_ptrace( thread ))
     {
         get_thread_context( thread, CONTEXT_CONTROL, &context );
-        resume_thread( thread );
+        resume_after_ptrace( thread );
     }
     return (void *)context.Eip;
 }
@@ -576,7 +576,7 @@ DECL_HANDLER(get_thread_context)
         if (flags && suspend_for_ptrace( thread ))
         {
             get_thread_context( thread, flags, data );
-            resume_thread( thread );
+            resume_after_ptrace( thread );
         }
     }
     release_object( thread );
@@ -604,7 +604,7 @@ DECL_HANDLER(set_thread_context)
         if (flags && suspend_for_ptrace( thread ))
         {
             set_thread_context( thread, flags, get_req_data() );
-            resume_thread( thread );
+            resume_after_ptrace( thread );
         }
         release_object( thread );
     }
diff --git a/server/context_powerpc.c b/server/context_powerpc.c
index b1dde4ff792..b6a2598881d 100644
--- a/server/context_powerpc.c
+++ b/server/context_powerpc.c
@@ -252,7 +252,7 @@ void *get_thread_ip( struct thread *thread )
     if (suspend_for_ptrace( thread ))
     {
         get_thread_context( thread, CONTEXT_CONTROL, &context );
-        resume_thread( thread );
+        resume_after_ptrace( thread );
     }
     return (void *)context.Iar;
 }
@@ -293,7 +293,7 @@ DECL_HANDLER(get_thread_context)
         if (flags && suspend_for_ptrace( thread ))
         {
             get_thread_context( thread, flags, data );
-            resume_thread( thread );
+            resume_after_ptrace( thread );
         }
     }
     release_object( thread );
@@ -321,7 +321,7 @@ DECL_HANDLER(set_thread_context)
         if (flags && suspend_for_ptrace( thread ))
         {
             set_thread_context( thread, flags, get_req_data() );
-            resume_thread( thread );
+            resume_after_ptrace( thread );
         }
         release_object( thread );
     }
diff --git a/server/context_sparc.c b/server/context_sparc.c
index bc1b3afbf23..20b4a26f45f 100644
--- a/server/context_sparc.c
+++ b/server/context_sparc.c
@@ -164,7 +164,7 @@ void *get_thread_ip( struct thread *thread )
     if (suspend_for_ptrace( thread ))
     {
         get_thread_context( thread, CONTEXT_CONTROL, &context );
-        resume_thread( thread );
+        resume_after_ptrace( thread );
     }
     return (void *)context.pc;
 }
@@ -199,7 +199,7 @@ DECL_HANDLER(get_thread_context)
         if (flags && suspend_for_ptrace( thread ))
         {
             get_thread_context( thread, flags, data );
-            resume_thread( thread );
+            resume_after_ptrace( thread );
         }
     }
     release_object( thread );
@@ -227,7 +227,7 @@ DECL_HANDLER(set_thread_context)
         if (flags && suspend_for_ptrace( thread ))
         {
             set_thread_context( thread, flags, get_req_data() );
-            resume_thread( thread );
+            resume_after_ptrace( thread );
         }
         release_object( thread );
     }
diff --git a/server/process.c b/server/process.c
index c3cf4366d7f..96482ebc882 100644
--- a/server/process.c
+++ b/server/process.c
@@ -673,11 +673,7 @@ void resume_process( struct process *process )
         while (thread)
         {
             struct thread *next = thread->proc_next;
-            if (!thread->suspend)
-            {
-                continue_thread( thread );
-                wake_thread( thread );
-            }
+            if (!thread->suspend) wake_thread( thread );
             thread = next;
         }
     }
@@ -781,7 +777,7 @@ static int read_process_memory( struct process *process, const int *addr, size_t
             if (read_thread_int( thread, addr++, dest++ ) == -1) break;
             len--;
         }
-        resume_thread( thread );
+        resume_after_ptrace( thread );
     }
     return !len;
 }
@@ -842,7 +838,7 @@ static void write_process_memory( struct process *process, int *addr, size_t len
         if (write_thread_int( thread, addr, *src, last_mask ) == -1) goto done;
 
     done:
-        resume_thread( thread );
+        resume_after_ptrace( thread );
     }
 }
 
diff --git a/server/ptrace.c b/server/ptrace.c
index b83ab7d4e27..33b71581d17 100644
--- a/server/ptrace.c
+++ b/server/ptrace.c
@@ -69,24 +69,20 @@ inline static int ptrace(int req, ...) { errno = EPERM; return -1; /*FAIL*/ }
 static const int use_ptrace = 1;  /* set to 0 to disable ptrace */
 
 /* handle a status returned by wait4 */
-static int handle_child_status( struct thread *thread, int pid, int status )
+static int handle_child_status( struct thread *thread, int pid, int status, int want_sig )
 {
     if (WIFSTOPPED(status))
     {
         int sig = WSTOPSIG(status);
         if (debug_level && thread)
             fprintf( stderr, "%04x: *signal* signal=%d\n", thread->id, sig );
-        switch(sig)
+        if (sig != want_sig)
         {
-        case SIGSTOP:  /* continue at once if not suspended */
-            if (thread && (thread->process->suspend + thread->suspend)) break;
-            /* fall through */
-        default:  /* ignore other signals for now */
+            /* ignore other signals for now */
             if (thread && get_thread_single_step( thread ))
                 ptrace( PTRACE_SINGLESTEP, pid, (caddr_t)1, sig );
             else
                 ptrace( PTRACE_CONT, pid, (caddr_t)1, sig );
-            break;
         }
         return sig;
     }
@@ -115,13 +111,13 @@ void sigchld_handler()
     for (;;)
     {
         if (!(pid = wait4( -1, &status, WUNTRACED | WNOHANG, NULL ))) break;
-        if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status );
+        if (pid != -1) handle_child_status( get_thread_from_pid(pid), pid, status, -1 );
         else break;
     }
 }
 
 /* wait for a ptraced child to get a certain signal */
-void wait4_thread( struct thread *thread, int signal )
+static void wait4_thread( struct thread *thread, int signal )
 {
     int res, status;
 
@@ -129,10 +125,15 @@ void wait4_thread( struct thread *thread, int signal )
     {
         if ((res = wait4( thread->unix_pid, &status, WUNTRACED, NULL )) == -1)
         {
-            perror( "wait4" );
+            if (errno == ECHILD)  /* must have died */
+            {
+                thread->unix_pid = -1;
+                thread->attached = 0;
+            }
+            else perror( "wait4" );
             return;
         }
-        res = handle_child_status( thread, res, status );
+        res = handle_child_status( thread, res, status, signal );
     } while (res && res != signal);
 }
 
@@ -176,66 +177,48 @@ void detach_thread( struct thread *thread, int sig )
     if (thread->attached)
     {
         /* make sure it is stopped */
-        suspend_thread( thread, 0 );
+        suspend_for_ptrace( thread );
         if (sig) send_thread_signal( thread, sig );
         if (thread->unix_pid == -1) return;
         if (debug_level) fprintf( stderr, "%04x: *detached*\n", thread->id );
         ptrace( PTRACE_DETACH, thread->unix_pid, (caddr_t)1, sig );
-        thread->suspend = 0;  /* detach makes it continue */
         thread->attached = 0;
     }
-    else
-    {
-        if (sig) send_thread_signal( thread, sig );
-        if (thread->suspend + thread->process->suspend) continue_thread( thread );
-    }
-}
-
-/* stop a thread (at the Unix level) */
-void stop_thread( struct thread *thread )
-{
-    /* can't stop a thread while initialisation is in progress */
-    if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) return;
-    /* first try to attach to it */
-    if (!thread->attached)
-        if (attach_thread( thread )) return;  /* this will have stopped it */
-    /* attached already, or attach failed -> send a signal */
-    if (thread->unix_pid == -1) return;
-    send_thread_signal( thread, SIGSTOP );
-    if (thread->attached) wait4_thread( thread, SIGSTOP );
-}
-
-/* make a thread continue (at the Unix level) */
-void continue_thread( struct thread *thread )
-{
-    if (thread->unix_pid == -1) return;
-    if (!thread->attached) send_thread_signal( thread, SIGCONT );
-    else ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
-                 thread->unix_pid, (caddr_t)1, SIGSTOP );
+    else if (sig) send_thread_signal( thread, sig );
 }
 
 /* suspend a thread to allow using ptrace on it */
-/* you must do a resume_thread when finished with the thread */
+/* you must do a resume_after_ptrace when finished with the thread */
 int suspend_for_ptrace( struct thread *thread )
 {
-    if (thread->attached)
-    {
-        suspend_thread( thread, 0 );
-        return 1;
-    }
     /* can't stop a thread while initialisation is in progress */
     if (thread->unix_pid == -1 || !is_process_init_done(thread->process)) goto error;
-    thread->suspend++;
+
+    if (thread->attached)
+    {
+        send_thread_signal( thread, SIGSTOP );
+        wait4_thread( thread, SIGSTOP );
+        return 1;
+    }
     if (attach_thread( thread )) return 1;
-    thread->suspend--;
  error:
     set_error( STATUS_ACCESS_DENIED );
     return 0;
 }
 
+/* resume a thread after we have used pthread on it */
+void resume_after_ptrace( struct thread *thread )
+{
+    if (thread->unix_pid == -1) return;
+    assert( thread->attached );
+    ptrace( get_thread_single_step(thread) ? PTRACE_SINGLESTEP : PTRACE_CONT,
+            thread->unix_pid, (caddr_t)1, 0 /* cancel the SIGSTOP */ );
+}
+
 /* read an int from a thread address space */
 int read_thread_int( struct thread *thread, const int *addr, int *data )
 {
+    errno = 0;
     *data = ptrace( PTRACE_PEEKDATA, thread->unix_pid, (caddr_t)addr, 0 );
     if ( *data == -1 && errno)
     {
diff --git a/server/thread.c b/server/thread.c
index 7e4ae690699..5d41a4a8ab5 100644
--- a/server/thread.c
+++ b/server/thread.c
@@ -301,11 +301,18 @@ static void set_thread_info( struct thread *thread,
     }
 }
 
+/* stop a thread (at the Unix level) */
+void stop_thread( struct thread *thread )
+{
+    /* can't stop a thread while initialisation is in progress */
+    if (is_process_init_done(thread->process)) send_thread_signal( thread, SIGUSR1 );
+}
+
 /* suspend a thread */
-int suspend_thread( struct thread *thread, int check_limit )
+static int suspend_thread( struct thread *thread )
 {
     int old_count = thread->suspend;
-    if (thread->suspend < MAXIMUM_SUSPEND_COUNT || !check_limit)
+    if (thread->suspend < MAXIMUM_SUSPEND_COUNT)
     {
         if (!(thread->process->suspend + thread->suspend++)) stop_thread( thread );
     }
@@ -314,16 +321,12 @@ int suspend_thread( struct thread *thread, int check_limit )
 }
 
 /* resume a thread */
-int resume_thread( struct thread *thread )
+static int resume_thread( struct thread *thread )
 {
     int old_count = thread->suspend;
     if (thread->suspend > 0)
     {
-        if (!(--thread->suspend + thread->process->suspend))
-        {
-            continue_thread( thread );
-            wake_thread( thread );
-        }
+        if (!(--thread->suspend + thread->process->suspend)) wake_thread( thread );
     }
     return old_count;
 }
@@ -500,6 +503,7 @@ static void thread_timeout( void *ptr )
 
     wait->user = NULL;
     if (thread->wait != wait) return; /* not the top-level wait, ignore it */
+    if (thread->suspend + thread->process->suspend > 0) return;  /* suspended, ignore it */
 
     if (debug_level) fprintf( stderr, "%04x: *wakeup* signaled=%d cookie=%p\n",
                               thread->id, STATUS_TIMEOUT, cookie );
@@ -722,7 +726,7 @@ static void get_selector_entry( struct thread *thread, int entry,
         if (read_thread_int( thread, addr, (int *)flags_buf ) == -1) goto done;
         *flags = flags_buf[entry & 3];
     done:
-        resume_thread( thread );
+        resume_after_ptrace( thread );
     }
 }
 
@@ -933,7 +937,7 @@ DECL_HANDLER(suspend_thread)
     if ((thread = get_thread_from_handle( req->handle, THREAD_SUSPEND_RESUME )))
     {
         if (thread->state == TERMINATED) set_error( STATUS_ACCESS_DENIED );
-        else reply->count = suspend_thread( thread, 1 );
+        else reply->count = suspend_thread( thread );
         release_object( thread );
     }
 }
diff --git a/server/thread.h b/server/thread.h
index 6e244c6c1a5..bf83f0c0998 100644
--- a/server/thread.h
+++ b/server/thread.h
@@ -110,8 +110,7 @@ extern struct thread *create_thread( int fd, struct process *process );
 extern struct thread *get_thread_from_id( thread_id_t id );
 extern struct thread *get_thread_from_handle( obj_handle_t handle, unsigned int access );
 extern struct thread *get_thread_from_pid( int pid );
-extern int suspend_thread( struct thread *thread, int check_limit );
-extern int resume_thread( struct thread *thread );
+extern void stop_thread( struct thread *thread );
 extern int wake_thread( struct thread *thread );
 extern int add_queue( struct object *obj, struct wait_queue_entry *entry );
 extern void remove_queue( struct object *obj, struct wait_queue_entry *entry );
@@ -127,11 +126,9 @@ extern struct thread_snapshot *thread_snap( int *count );
 /* ptrace functions */
 
 extern void sigchld_handler();
-extern void wait4_thread( struct thread *thread, int signal );
-extern void stop_thread( struct thread *thread );
-extern void continue_thread( struct thread *thread );
 extern void detach_thread( struct thread *thread, int sig );
 extern int suspend_for_ptrace( struct thread *thread );
+extern void resume_after_ptrace( struct thread *thread );
 extern int read_thread_int( struct thread *thread, const int *addr, int *data );
 extern int write_thread_int( struct thread *thread, int *addr, int data, unsigned int mask );
 extern void *get_thread_ip( struct thread *thread );
diff --git a/server/trace.c b/server/trace.c
index 65d05cf7499..1e09f62f102 100644
--- a/server/trace.c
+++ b/server/trace.c
@@ -195,6 +195,11 @@ static void dump_varargs_unicode_str( size_t size )
 
 static void dump_varargs_context( size_t size )
 {
+    if (!size)
+    {
+        fprintf( stderr, "{}" );
+        return;
+    }
     dump_context( cur_data );
     remove_data( size );
 }
@@ -202,6 +207,12 @@ static void dump_varargs_context( size_t size )
 static void dump_varargs_exc_event( size_t size )
 {
     const CONTEXT *ptr = cur_data;
+
+    if (!size)
+    {
+        fprintf( stderr, "{}" );
+        return;
+    }
     fprintf( stderr, "{context=" );
     dump_context( ptr );
     fprintf( stderr, ",rec=" );