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[binutils-gdb] Document possible unreliability of '$_ret'


https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=45fa2529db961adff41c52c3a560808cb135beb2

commit 45fa2529db961adff41c52c3a560808cb135beb2
Author: Pedro Alves <palves@redhat.com>
Date:   Tue Mar 15 11:08:52 2016 +0000

    Document possible unreliability of '$_ret'
    
    gdb/doc/ChangeLog:
    2016-03-15  Pedro Alves  <palves@redhat.com>
    	    Andreas Arnez  <arnez@linux.vnet.ibm.com>
    	    Marcin KoÅ?cielnicki  <koriakin@0x04.net>
    
    	* gdb.texinfo (Tracepoint Actions): Document possible
    	unreliability of '$_ret'.

Diff:
---
 gdb/doc/ChangeLog   | 7 +++++++
 gdb/doc/gdb.texinfo | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 3d49085..0606d9d 100644
--- 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 KoÅ?cielnicki  <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 bf7df35..5f88335 100644
--- 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.


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