Move declarations related to process stopping handler to a new file trace.h
diff --git a/sysdeps/linux-gnu/Makefile.am b/sysdeps/linux-gnu/Makefile.am
index bd52092..e6fd7ef 100644
--- a/sysdeps/linux-gnu/Makefile.am
+++ b/sysdeps/linux-gnu/Makefile.am
@@ -28,7 +28,8 @@
 noinst_HEADERS = \
 	arch_syscallent.h \
 	signalent1.h \
-	syscallent1.h
+	syscallent1.h \
+	trace.h
 
 EXTRA_DIST = \
 	arch_mksyscallent \
diff --git a/sysdeps/linux-gnu/trace.c b/sysdeps/linux-gnu/trace.c
index af9423c..dfa5126 100644
--- a/sysdeps/linux-gnu/trace.c
+++ b/sysdeps/linux-gnu/trace.c
@@ -19,6 +19,7 @@
 #include "common.h"
 #include "breakpoint.h"
 #include "proc.h"
+#include "linux-gnu/trace.h"
 
 /* If the system headers did not provide the constants, hard-code the normal
    values.  */
@@ -200,70 +201,6 @@
 		      "putting off the continue, events in que.");
 }
 
-/**
- * This is used for bookkeeping related to PIDs that the event
- * handlers work with.
- */
-struct pid_task {
-	pid_t pid;	/* This may be 0 for tasks that exited
-			 * mid-handling.  */
-	int sigstopped : 1;
-	int got_event : 1;
-	int delivered : 1;
-	int vforked : 1;
-	int sysret : 1;
-} * pids;
-
-struct pid_set {
-	struct pid_task * tasks;
-	size_t count;
-	size_t alloc;
-};
-
-/**
- * Breakpoint re-enablement.  When we hit a breakpoint, we must
- * disable it, single-step, and re-enable it.  That single-step can be
- * done only by one task in a task group, while others are stopped,
- * otherwise the processes would race for who sees the breakpoint
- * disabled and who doesn't.  The following is to keep track of it
- * all.
- */
-struct process_stopping_handler
-{
-	struct event_handler super;
-
-	/* The task that is doing the re-enablement.  */
-	Process *task_enabling_breakpoint;
-
-	/* The pointer being re-enabled.  */
-	struct breakpoint *breakpoint_being_enabled;
-
-	/* Artificial atomic skip breakpoint, if any needed.  */
-	void *atomic_skip_bp_addr;
-
-	/* When all tasks are stopped, this callback gets called.  */
-	void (*on_all_stopped)(struct process_stopping_handler *);
-
-	enum {
-		/* We are waiting for everyone to land in t/T.  */
-		psh_stopping = 0,
-
-		/* We are doing the PTRACE_SINGLESTEP.  */
-		psh_singlestep,
-
-		/* We are waiting for all the SIGSTOPs to arrive so
-		 * that we can sink them.  */
-		psh_sinking,
-
-		/* This is for tracking the ugly workaround.  */
-		psh_ugly_workaround,
-	} state;
-
-	int exiting;
-
-	struct pid_set pids;
-};
-
 static struct pid_task *
 get_task_info(struct pid_set * pids, pid_t pid)
 {
diff --git a/sysdeps/linux-gnu/trace.h b/sysdeps/linux-gnu/trace.h
new file mode 100644
index 0000000..040a235
--- /dev/null
+++ b/sysdeps/linux-gnu/trace.h
@@ -0,0 +1,97 @@
+/*
+ * This file is part of ltrace.
+ * Copyright (C) 2011,2012 Petr Machata, Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#ifndef _LTRACE_LINUX_TRACE_H_
+#define _LTRACE_LINUX_TRACE_H_
+
+/* This publishes some Linux-specific data structures used for process
+ * handling.  */
+
+/**
+ * This is used for bookkeeping related to PIDs that the event
+ * handlers work with.
+ */
+struct pid_task {
+	pid_t pid;	/* This may be 0 for tasks that exited
+			 * mid-handling.  */
+	int sigstopped : 1;
+	int got_event : 1;
+	int delivered : 1;
+	int vforked : 1;
+	int sysret : 1;
+};
+
+struct pid_set {
+	struct pid_task *tasks;
+	size_t count;
+	size_t alloc;
+};
+
+/**
+ * Breakpoint re-enablement.  When we hit a breakpoint, we must
+ * disable it, single-step, and re-enable it.  That single-step can be
+ * done only by one task in a task group, while others are stopped,
+ * otherwise the processes would race for who sees the breakpoint
+ * disabled and who doesn't.  The following is to keep track of it
+ * all.
+ */
+struct process_stopping_handler
+{
+	struct event_handler super;
+
+	/* The task that is doing the re-enablement.  */
+	Process *task_enabling_breakpoint;
+
+	/* The pointer being re-enabled.  */
+	struct breakpoint *breakpoint_being_enabled;
+
+	/* Artificial atomic skip breakpoint, if any needed.  */
+	void *atomic_skip_bp_addr;
+
+	/* When all tasks are stopped, this callback gets called.  */
+	void (*on_all_stopped)(struct process_stopping_handler *);
+
+	enum {
+		/* We are waiting for everyone to land in t/T.  */
+		psh_stopping = 0,
+
+		/* We are doing the PTRACE_SINGLESTEP.  */
+		psh_singlestep,
+
+		/* We are waiting for all the SIGSTOPs to arrive so
+		 * that we can sink them.  */
+		psh_sinking,
+
+		/* This is for tracking the ugly workaround.  */
+		psh_ugly_workaround,
+	} state;
+
+	int exiting;
+
+	struct pid_set pids;
+};
+
+/* Allocate a process stopping handler, initialize it and install it.
+ * Return 0 on success or a negative value on failure.  */
+int process_install_stopping_handler
+	(struct Process *proc, struct breakpoint *sbp,
+	 void (*cb)(struct process_stopping_handler *));
+
+#endif /* _LTRACE_LINUX_TRACE_H_ */