Fix PR19548: Breakpoint re-set inserts breakpoints when it shouldn't

PR19548 shows that we still have problems related to 13fd3ff34329:

 [PR17431: following execs with "breakpoint always-inserted on"]
 https://sourceware.org/ml/gdb-patches/2014-09/msg00733.html

The problem this time is that we currently update the global location
list and try to insert breakpoint locations after re-setting _each_
breakpoint in turn.

Say:

 - We have _more_ than one breakpoint set.  Let's assume 2.

 - There's a breakpoint with a pre-exec address that ends up being an
   unmapped address after the exec.

 - That breakpoint is NOT the first in the breakpoint list.

Then when handling an exec, and we re-set the first breakpoint in the
breakpoint list, we mistakently try to install the old pre-exec /
un-re-set locations of the other breakpoint, which fails:

 (gdb) continue
 Continuing.
 process 28295 is executing new program: (...)/execl-update-breakpoints2
 Error in re-setting breakpoint 1: Warning:
 Cannot insert breakpoint 2.
 Cannot access memory at address 0x1000764

 Breakpoint 1, main (argc=1, argv=0x7fffffffd368) at /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.base/execl-update-breakpoints.c:34
 34        len = strlen (argv[0]);
 (gdb)

Fix this by deferring the global location list update till after all
breakpoints are re-set.

Tested on x86_64 Fedora 20, native and gdbserver.

gdb/ChangeLog:
2016-02-09  Pedro Alves  <palves@redhat.com>

	PR breakpoints/19548
	* breakpoint.c (create_overlay_event_breakpoint): Don't update
	global location list here.
	(create_longjmp_master_breakpoint)
	(create_std_terminate_master_breakpoint)
	(create_exception_master_breakpoint, create_jit_event_breakpoint)
	(update_breakpoint_locations):
	(breakpoint_re_set): Update global location list after all
	breakpoints are re-set.

gdb/testsuite/ChangeLog:
2016-02-09  Pedro Alves  <palves@redhat.com>

	PR breakpoints/19548
	* gdb.base/execl-update-breakpoints.c (some_function): New
	function.
	(main): Call it.
	* gdb.base/execl-update-breakpoints.exp: Add a second breakpoint.
	Tighten expected GDB output.

3 files changed, 44 insertions, 2 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 2a71930..f8e0800 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,12 @@
+2016-02-09  Pedro Alves  <palves@redhat.com>
+
+	PR breakpoints/19548
+	* gdb.base/execl-update-breakpoints.c (some_function): New
+	function.
+	(main): Call it.
+	* gdb.base/execl-update-breakpoints.exp: Add a second breakpoint.
+	Tighten expected GDB output.
+
 2016-02-08  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* Makefile.in (ALL_SUBDIRS): Remove.
diff --git a/gdb/testsuite/gdb.base/execl-update-breakpoints.c b/gdb/testsuite/gdb.base/execl-update-breakpoints.c
index 3978a70..38f1cea 100644
--- a/gdb/testsuite/gdb.base/execl-update-breakpoints.c
+++ b/gdb/testsuite/gdb.base/execl-update-breakpoints.c
@@ -20,6 +20,11 @@
 #include <stdlib.h>
 #include <string.h>
 
+void
+some_function (void)
+{
+}
+
 int
 main (int argc, char **argv)
 {
@@ -34,5 +39,6 @@ main (int argc, char **argv)
 
   execl (bin, bin, (char *) NULL);
   perror ("execl failed");
+  some_function ();
   exit (1);
 }
diff --git a/gdb/testsuite/gdb.base/execl-update-breakpoints.exp b/gdb/testsuite/gdb.base/execl-update-breakpoints.exp
index 4f35999..47a848e 100644
--- a/gdb/testsuite/gdb.base/execl-update-breakpoints.exp
+++ b/gdb/testsuite/gdb.base/execl-update-breakpoints.exp
@@ -96,6 +96,7 @@ if {!$cannot_access} {
 
 proc test { always_inserted } {
     global exec1
+    global gdb_prompt
 
     clean_restart ${exec1}
 
@@ -106,13 +107,39 @@ proc test { always_inserted } {
 	return -1
     }
 
-    # On a buggy GDB, with always-inserted on, we'd see:
+    # Set a second breakpoint (whose original address also ends up
+    # unmmapped after the exec), for PR 19548.
+    gdb_test "break some_function" "Breakpoint .*"
+
+    # PR17431: with always-inserted on, we'd see:
     #  (gdb) continue
     #  Continuing.
     #  Warning:
     #  Cannot insert breakpoint 1.
     #  Cannot access memory at address 0x10000ff
-    gdb_test "continue" "Breakpoint 1, main.*" "continue across exec"
+
+    # PR 19548: with more than one breakpoint, we'd see:
+    #  (gdb) continue
+    #  Continuing.
+    #  process (...) is executing new program: (...)/execl-update-breakpoints2
+    #  Error in re-setting breakpoint 1: Warning:
+    #  Cannot insert breakpoint 2.
+    #  Cannot access memory at address 0x1000764
+    set not_nl "\[^\r\n\]*"
+    set regex ""
+    append regex \
+	"^continue\r\n" \
+	"Continuing\\.\r\n" \
+	"${not_nl} is executing new program: ${not_nl}\r\n" \
+	"(Reading ${not_nl} from remote target\\.\\.\\.\r\n)*" \
+	"\r\n" \
+	"Breakpoint 1, main.*$gdb_prompt $"
+    set message "continue across exec"
+    gdb_test_multiple "continue" $message {
+	-re $regex {
+	    pass $message
+	}
+    }
 }
 
 foreach always_inserted { "off" "on" } {