* lisp/emacs-lisp/generator.el (cps--make-dynamic-binding-wrapper):
Remove extra evaluation of form.
* test/lisp/emacs-lisp/generator-tests.el
(cps-iter-lambda-with-dynamic-binding): New test.

* lisp/net/tramp.el (tramp-file-name-for-operation):
Add `file-system-info'.

* lisp/net/tramp-adb.el (tramp-adb-handle-file-system-info): New defun.
(tramp-adb-file-name-handler-alist): Use it.

* lisp/net/tramp-gvfs.el (tramp-gvfs-file-system-attributes)
(tramp-gvfs-file-system-attributes-regexp): New defconst.
(tramp-gvfs-handle-file-system-info): New defun.
(tramp-gvfs-file-name-handler-alist): Use it.
(tramp-gvfs-get-directory-attributes): Fix property name.
(tramp-gvfs-get-root-attributes): Support also file system attributes.

* lisp/net/tramp-sh.el (tramp-sh-handle-file-system-info): New defun.
(tramp-sh-file-name-handler-alist): Use it.
(tramp-sh-handle-insert-directory): Insert size information.
(tramp-get-remote-df): New defun.

* lisp/net/tramp-smb.el (tramp-smb-handle-file-system-info): New defun.
(tramp-smb-file-name-handler-alist): Use it.
(tramp-smb-handle-insert-directory): Insert size information.

* test/lisp/net/tramp-tests.el (tramp-test37-file-system-info):
New test.
(tramp-test38-asynchronous-requests)
(tramp-test39-recursive-load, tramp-test40-remote-load-path)
(tramp-test41-unload): Rename.

Rewrote a significant part of the Flymake backend API.  Flymake now
ignores the return value of backend functions: a function can either
returns or errors.  If it doesn't error, a backend is no longer
constrained to call REPORT-FN exactly once.  It may do so any number
of times, cumulatively reporting diagnostics.  Flymake keeps track of
outdated REPORT-FN instances and disconsiders obsolete reports.
Backends should avoid reporting obsolete data by cancelling any
ongoing processing at every renewed call to the backend function.

Consolidated flymake.el internal data structures to require less
buffer-local variables.  Adjusted Flymake's mode-line indicator to the
new semantics.

Adapted and simplified the implementation of elisp and legacy
backends, fixing potential race conditions when calling backends in
rapid succession.

Added a new test for a backend that calls REPORT-FN multiple
times.  Simplify test infrastructure.

* lisp/progmodes/flymake-elisp.el (flymake-elisp-checkdoc)
(flymake-elisp-byte-compile): Error instead of returning nil
if not in emacs-lisp-mode.
(flymake-elisp--byte-compile-process): New buffer-local variable.
(flymake-elisp-byte-compile): Mark (and kill) previous process
obsolete process before starting a new one.  Don't report if
obsolete process.

* lisp/progmodes/flymake-proc.el
(flymake-proc--current-process): New buffer-local variable.
(flymake-proc--processes): Remove.
(flymake-proc--process-filter): Don't bind
flymake-proc--report-fn.
(flymake-proc--process-sentinel): Rewrite.  Don't report if
obsolete process.
(flymake-proc-legacy-flymake): Rewrite.  Mark (and kill)
previous process obsolete process before starting a new
one.  Integrate flymake-proc--start-syntax-check-process
helper.
(flymake-proc--start-syntax-check-process): Delete.
(flymake-proc-stop-all-syntax-checks): Don't use
flymake-proc--processes, iterate buffers.
(flymake-proc-compile):

* lisp/progmodes/flymake.el (subr-x): Require it
explicitly.
(flymake-diagnostic-functions): Reword docstring.
(flymake--running-backends, flymake--disabled-backends)
(flymake--diagnostics-table): Delete.
(flymake--backend-state): New buffer-local variable and new defstruct.
(flymake--with-backend-state, flymake--collect)
(flymake-running-backends, flymake-disabled-backends)
(flymake-reporting-backends): New helpers.
(flymake-is-running): Use flymake-running-backends.
(flymake--handle-report): Rewrite.
(flymake-make-report-fn): Ensure REPORT-FN runs in the correct
buffer or not at all.
(flymake--disable-backend, flymake--run-backend): Rewrite.
(flymake-start): Rewrite.
(flymake-mode): Set flymake--backend-state.
(flymake--mode-line-format): Rewrite.

* test/lisp/progmodes/flymake-tests.el
(flymake-tests--wait-for-backends): New helper.
(flymake-tests--call-with-fixture): Use it.
(included-c-header-files): Fix whitespace.
(flymake-tests--diagnose-words): New helper.
(dummy-backends): Rewrite for new semantics.  Use cl-letf.
(flymake-tests--assert-set): Use quote.
(recurrent-backend): New test.

The first of these problems is longstanding: if an error-less B.h is
included from error-ridden A.h, flymake's legacy parser will panic
(and disable itself) since it sees a non-zero exit for a clean file.
To fix this, recommend returning 'true' in the documentation for the
check-syntax target.

Another problem was introduced by the parser rewrite.  For error
patterns spanning more than one line, point may be left in the middle
of a line and thus render other patterns useless.  Those patterns were
written for the old line-by-line parser.  To make them useful again,
move to the beginning of line in those situations.

The third problem was also longstanding and happened on newer GCC's:
The "In file included from" prefix confused
flymake-proc-get-real-file-name.  Fix this.

Also updated flymake--diag-region to fallback to highlighting a full
line less often.

Add automatic tests to check this.

* lisp/progmodes/flymake-proc.el
(flymake-proc--diagnostics-for-pattern): Fix bug when patterns
accidentally spans more than one line.  Don't create
diagnostics without error messages.
(flymake-proc-real-file-name-considering-includes): New
helper.
(flymake-proc-allowed-file-name-masks): Use it.

* lisp/progmodes/flymake.el (flymake-diag-region): Make COL
argument explicitly optional.  Only fall back to full line in extreme
cases.

* test/lisp/progmodes/flymake-tests.el
(included-c-header-files): New test.
(different-diagnostic-types): Update.

* test/lisp/progmodes/flymake-resources/Makefile
(check-syntax): Always return success (0) error code.
(CC_OPTS): Add -Wextra

* test/lisp/progmodes/flymake-resources/errors-and-warnings.c
(main): Rewrite comments.

* test/lisp/progmodes/flymake-resources/errors-and-warnings.c:
Include some dummy header files.

* test/lisp/progmodes/flymake-resources/no-problems.h: New file.

* test/lisp/progmodes/flymake-resources/some-problems.h: New file.

* doc/misc/flymake.texi (Example---Configuring a tool called
via make): Recommend adding "|| true" to the check-syntax target.

Add filters, useful for backends like the upcoming
flymake-elisp-checkdoc backend, for example, which litters everything
with low-priority notes.

Also re-implement wraparound for flymake-goto-next-error. Manual
mentions this, so it's probably a good idea to keep it.  Added a new
customization variable flymake-wrap-around to control it.

* lisp/progmodes/flymake.el (flymake-goto-prev-error)
(flymake-goto-next-error): Accept FILTER argument.
(flymake-wrap-around): New variable.
(flymake-goto-next-error): Wrap around according to flymake-wrap-around.

* test/lisp/progmodes/flymake-tests.el
(different-diagnostic-types, dummy-backends): Pass FILTER to
flymake-goto-prev-error.
(different-diagnostic-types)
(dummy-backends): Use flymake-wrap-around.

Use display-warning and a dedicated *Flymake log* buffer.

To ease readability, flymake log messages are now prefixed with a
common prefix and the buffer that originated them.

Some situations of over-zealous logging are fixed.

Use byte-compiler info, if available, to determine whence the
flymake-related log message is coming.

* lisp/progmodes/flymake-proc.el
(flymake-proc--diagnostics-for-pattern): Improve log message.
(flymake-proc--panic): Always flymake-log an error
(flymake-proc--safe-delete-file)
(flymake-proc--safe-delete-directory):
Downgrade warning
(flymake-proc-start-syntax-check): Simplify slightly.
(flymake-proc--start-syntax-check-process): Simplify.
(flymake-proc--init-find-buildfile-dir)
(flymake-proc--init-create-temp-source-and-master-buffer-copy):
No need to warn twice.

* lisp/progmodes/flymake.el (flymake-log): Convert to macro.
(flymake--log-1): New helper.
(flymake-log-level): Deprecate.
(flymake-error): New helper.
(flymake-ler-make-ler, flymake--handle-report, flymake-mode):
Use flymake-error.
(flymake-on-timer-event)
(flymake--handle-report, flymake--disable-backend)
(flymake--run-backend, flymake-start, flymake-mode-on)
(flymake-mode-off, flymake-after-change-function)
(flymake-after-save-hook, flymake-find-file-hook): Adjust
flymake-log calls.

* test/lisp/progmodes/flymake-tests.el
(flymake-tests--call-with-fixture): Only log errors.

Lay groundwork for multiple active backends in the same buffer.

Backends are lisp functions called when flymake-mode sees fit.  They
are responsible for examining the current buffer and telling
flymake.el, via return value, if they can syntax check it.
Backends should return quickly and inexpensively, but they are also
passed a REPORT-FN argument which they may or may not call
asynchronously after performing more expensive work.

REPORT-FN's calling convention stipulates that a backend calls it with
a list of diagnostics as argument, or, alternatively, with a symbol
denoting an exceptional situation, usually some panic resulting from a
misconfigured backend.  In keeping with legacy behaviour,
flymake.el's response to a panic is to disable the issuing backend.

The flymake--diag object representing a diagnostic now also keeps
information about its source backend.  Among other uses, this allows
flymake to selectively cleanup overlays based on which backend is
updating its diagnostics.

* lisp/progmodes/flymake-proc.el (flymake-proc--report-fn):
New dynamic variable.
(flymake-proc--process): New variable.
(flymake-can-syntax-check-buffer): Remove.
(flymake-proc--process-sentinel): Simplify.  Use
unwind-protect.  Affect flymake-proc--processes here.
Bind flymake-proc--report-fn.
(flymake-proc--process-filter): Bind flymake-proc--report-fn.
(flymake-proc--post-syntax-check): Delete
(flymake-proc-start-syntax-check): Take mandatory
report-fn.  Rewrite.  Bind flymake-proc--report-fn.
(flymake-proc--process-sentinel): Rewrite and simplify.
(flymake-proc--panic): New helper.
(flymake-proc--start-syntax-check-process): Record report-fn
in process.  Use flymake-proc--panic.
(flymake-proc-stop-all-syntax-checks): Use mapc.  Don't affect
flymake-proc--processes here.  Record interruption reason.
(flymake-proc--init-find-buildfile-dir)
(flymake-proc--init-create-temp-source-and-master-buffer-copy):
Use flymake-proc--panic.
(flymake-diagnostic-functions): Add
flymake-proc-start-syntax-check.
(flymake-proc-compile): Call
flymake-proc-stop-all-syntax-checks with a reason.

* lisp/progmodes/flymake.el (flymake-backends): Delete.
(flymake-check-was-interrupted): Delete.
(flymake--diag): Add backend slot.
(flymake-delete-own-overlays): Take optional filter arg.
(flymake-diagnostic-functions): New user-visible variable.
(flymake--running-backends, flymake--disabled-backends): New
buffer-local variables.
(flymake-is-running): Now a function, not a variable.
(flymake-mode-line, flymake-mode-line-e-w)
(flymake-mode-line-status): Delete.
(flymake-lighter):  flymake's minor-mode "lighter".
(flymake-report): Delete.
(flymake--backend): Delete.
(flymake--can-syntax-check-buffer): Delete.
(flymake--handle-report, flymake--disable-backend)
(flymake--run-backend, flymake--run-backend):  New helpers.
(flymake-make-report-fn): Make a lambda.
(flymake--start-syntax-check): Iterate
flymake-diagnostic-functions.
(flymake-mode): Use flymake-lighter.  Simplify.  Initialize
flymake--running-backends and flymake--disabled-backends.
(flymake-find-file-hook): Simplify.

* test/lisp/progmodes/flymake-tests.el
(flymake-tests--call-with-fixture): Use flymake-is-running the
function.  Check if flymake-mode already active before activating it.
Add a thorough test for flymake multiple backends

* lisp/progmodes/flymake.el (flymake--start-syntax-check):
Don't use condition-case-unless-debug, use condition-case

* test/lisp/progmodes/flymake-tests.el
(flymake-tests--assert-set): New helper macro.
(dummy-backends): New test.

* lisp/progmodes/flymake-proc.el
(flymake-proc--diagnostics-for-pattern): Rewrite (using cl-loop) to
honour more sophisticated flymake-proc-diagnostic-type-pred.
(flymake-warning-re): Is now an obsolete alias for
flymake-proc-diagnostic-type-pred.
(flymake-proc-diagnostic-type-pred): Rename and augment from
flymake-proc-warning-predicate.  (flymake-proc-warning-predicate):
Delete.

* lisp/progmodes/flymake.el (flymake-note): New face.
(flymake-diagnostic-types-alist): Simplify.
(flymake-note): New overlay category.
(flymake--lookup-type-property): Only lookup single keys, not lists.
(flymake--diag-errorp): Rewrite.
(flymake--highlight-line): Use flymake--lookup-type-property.

* test/lisp/progmodes/flymake-tests.el
(different-diagnostic-types): Rename from errors-and-warnings.
Check notes.
(flymake-tests--call-with-fixture): Use
flymake-proc-diagnostic-type-pred.

* test/lisp/progmodes/flymake-tests.el
(flymake-tests--call-with-fixture): Save excursion.
(errors-and-warnings): New test.

* test/lisp/progmodes/flymake-resources/errors-and-warnings.c:
New test fixture.