Document possible unreliability of '$_ret'

gdb/doc/ChangeLog:
2016-03-15  Pedro Alves  <palves@redhat.com>
	    Andreas Arnez  <arnez@linux.vnet.ibm.com>
	    Marcin Kościelnicki  <koriakin@0x04.net>

	* gdb.texinfo (Tracepoint Actions): Document possible
	unreliability of '$_ret'.

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 3d49085ed7d2d6a8cb1bdf7b866ed553f1b8cd4e..0606d9db2886a0bf9202aa18d51b82fd487d4215 100644 (file)
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,10 @@
+2016-03-15  Pedro Alves  <palves@redhat.com>
+           Andreas Arnez  <arnez@linux.vnet.ibm.com>
+           Marcin Kościelnicki  <koriakin@0x04.net>
+
+       * gdb.texinfo (Tracepoint Actions): Document possible
+       unreliability of '$_ret'.
+
 2016-03-11  Andrew Burgess  <andrew.burgess@embecosm.com>
 
        * gdb.texinfo (Symbols): Document new 'maint info line-table'

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index bf7df3557af92c27a636e32a45a85bbb5a7753c4..5f88335c737be26cd630683e94453686204692d1 100644 (file)
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -12878,6 +12878,13 @@ Collect all local variables.
 Collect the return address.  This is helpful if you want to see more
 of a backtrace.
 
+@emph{Note:} The return address location can not always be reliability
+determined up front, and the wrong address / registers may end up
+collected instead.  On some architectures the reliability is higher
+for tracepoints at function entry, while on others it's the opposite.
+When this happens, backtracing will stop because the return address is
+found unavailable (unless another collect rule happened to match it).
+
 @item $_probe_argc
 Collects the number of arguments from the static probe at which the
 tracepoint is located.