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Diffstat (limited to 'gdb/doc/gdb.texinfo')
| -rw-r--r-- | gdb/doc/gdb.texinfo | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 5e02172..e61bd7e 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -9938,6 +9938,16 @@ if you ask for a block so large that it goes past the bottom of the stack, the target agent may report an error trying to read from an invalid address. +@item +If you do not collect registers at a tracepoint, @value{GDBN} can +infer that the value of @code{$pc} must be the same as the address of +the tracepoint and use that when you are looking at a trace frame +for that tracepoint. However, this cannot work if the tracepoint has +multiple locations (for instance if it was set in a function that was +inlined), or if it has a @code{while-stepping} loop. In those cases +@value{GDBN} will warn you that it can't infer @code{$pc}, and default +it to zero. + @end itemize @node Analyze Collected Data @@ -10141,6 +10151,22 @@ gdb_long_test = 17 '\021' (@value{GDBP}) @end smallexample +@code{tdump} works by scanning the tracepoint's current collection +actions and printing the value of each expression listed. So +@code{tdump} can fail, if after a run, you change the tracepoint's +actions to mention variables that were not collected during the run. + +Also, for tracepoints with @code{while-stepping} loops, @code{tdump} +uses the collected value of @code{$pc} to distinguish between trace +frames that were collected at the tracepoint hit, and frames that were +collected while stepping. This allows it to correctly choose whether +to display the basic list of collections, or the collections from the +body of the while-stepping loop. However, if @code{$pc} was not collected, +then @code{tdump} will always attempt to dump using the basic collection +list, and may fail if a while-stepping frame does not include all the +same data that is collected at the tracepoint hit. +@c This is getting pretty arcane, example would be good. + @node save-tracepoints @subsection @code{save-tracepoints @var{filename}} @kindex save-tracepoints |