[Converted from Gnats 129] Re-do GDB's output pager. GDB's output pager still relies on people correctly using *_filtered for gdb_stdout and *_unfiltered for gdb_stdlog / gdb_stderr. Hopefully, with all normal output going to gdb_stdout, the pager can just look at the ui_file that the output is on and then use that to decide what to do about paging. Sounds good in theory. Release: unknown
*** Bug 17222 has been marked as a duplicate of this bug. ***
I looked into this a bit. There are a lot of bad uses of unfiltered output -- tedious but easy to fix, I've got a bunch of patches for that. The difficult part, I think, is that there are spots that use unfiltered output because the intervention of the pager at that moment could cause trouble. For example, targets may announce things when infrun is doing its thing, and it's not at all clear to me that this code is set up to handle a random quit(). You can look for print_thread_events to see some examples of what's being printed. One idea might be to let this sort of code protect itself by setting some global variable. This global would indicate that the pager should temporarily be disabled. Alternatively maybe these spots can be made quit-safe. Or, maybe I'm just mistaken about this. I'm in favor of implementing this idea, FWIW. I think it would remove a contribution / maintenance hurdle in gdb. It would probably simplify the pager code. Also we could finally make wrap_here a method on ui_file instead of this weird thing we currently have, where code sometimes does: wrap_here (" "); fputs_filtered (i == 0 ? ": " : ", ", stream); ... that is, mixes output to some parameterized stream with calls to wrap_here, which actually only works for stdout.
We already have set_batch_flag_and_restore_page_info for temporarily disabling the pager, so that part is solved. The question is more where to use it.
I have a series to get rid of this distinction and rely just on the stream.
The master branch has been updated by Tom Tromey <tromey@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=3cd5229387926dbd2fe842328e7d923bbb41322c commit 3cd5229387926dbd2fe842328e7d923bbb41322c Author: Tom Tromey <tom@tromey.com> Date: Sat Jan 1 13:18:17 2022 -0700 Change the pager to a ui_file This rewrites the output pager as a ui_file implementation. A new header is introduced to declare the pager class. The implementation remains in utils.c for the time being, because there are some static globals there that must be used by this code. (This could be cleaned up at some future date.) I went through all the text output in gdb to ensure that this change should be ok. There are a few cases: * Any existing call to printf_unfiltered is required to be avoid the pager. This is ensured directly in the implementation. * All remaining calls to the f*_unfiltered functions -- the ones that take an explicit ui_file -- either send to an unfiltered stream (e.g., gdb_stderr), which is obviously ok; or conditionally send to gdb_stdout I investigated all such calls by searching for: grep -e '\bf[a-z0-9_]*_unfiltered' *.[chyl] */*.[ch] | grep -v gdb_stdlog | grep -v gdb_stderr This yields a number of candidates to check. * The breakpoint _print_recreate family, and save_trace_state_variables. These are used for "save" commands and so are fine. * Things printing to a temporary stream. Obviously ok. * Disassembly selftests. * print_gdb_help - this is non-obvious, but ok because paging isn't yet enabled at this point during startup. * serial.c - doens't use gdb_stdout * The code in compile/. This is all printing to a file. * DWARF DIE dumping - doesn't reference gdb_stdout. * Calls to the _filtered form -- these are all clearly ok, because if they are using gdb_stdout, then filtering will still apply; and if not, then filtering never applied and still will not. Therefore, at this point, there is no longer any distinction between all the other _filtered and _unfiltered calls, and they can be unified. In this patch, take special note of the vfprintf_maybe_filtered and ui_file::vprintf change. This is one instance of the above idea, erasing the distinction between filtered and unfiltered -- in this part of the change, the "unfiltered_output" flag is never passe to cli_ui_out. Subsequent patches will go much further in this direction. Also note the can_emit_style_escape changes in ui-file.c. Checking against gdb_stdout or gdb_stderr was always a bit of a hack; and now it is no longer needed, because this is decision can be more fully delegated to the particular ui_file implementation. ui_file::can_page is removed, because this patch removed the only call to it. I think this is the main part of fixing PR cli/7234. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=7234
Fixed.