gdb testsuite: Introduce allow_fork_tests and use it throughoutusers/keiths/try-allow_fork_tests

Cygwin debugging does not support follow fork.  There is currently no
interface between the debugger and the Cygwin runtime to be able to
intercept forks and execs.  Consequently, testcases that try to
exercise fork/exec all FAIL, and several hit long cascading timeouts.

Add a new allow_fork_tests procedure, meant be be used with require,
and sprinkle it throughout testcases that exercise fork.

Note that some tests currently are skipped on targets other than
Linux, with something like:

 # Until "set follow-fork-mode" and "catch vfork" are implemented on
 # other targets...
 #
 if {![istarget "*-linux*"]} {
     continue
 }

However, some BSD ports also support fork debugging nowadays, and the
testcases were never adjusted...  That is why the new allow_fork_tests
procedure doesn't look for linux.

With this patch, on Cygwin, I get this:

 $ make check TESTS="*/*fork*.exp"

 ...
		 === gdb Summary ===

 # of expected passes            6
 # of untested testcases         1
 # of unsupported tests          31

Change-Id: I0c5e8c574d1f61b28d370c22a0b0b6bc3efaf978

31 files changed, 57 insertions, 29 deletions

diff --git a/gdb/testsuite/gdb.base/catch-fork-kill.exp b/gdb/testsuite/gdb.base/catch-fork-kill.exp
index 0fd853b..224a8df 100644
--- a/gdb/testsuite/gdb.base/catch-fork-kill.exp
+++ b/gdb/testsuite/gdb.base/catch-fork-kill.exp
@@ -32,6 +32,8 @@
 
 standard_testfile
 
+require allow_fork_tests
+
 # Build two programs -- one for fork, and another for vfork.
 set testfile_fork "${testfile}-fork"
 set testfile_vfork "${testfile}-vfork"
diff --git a/gdb/testsuite/gdb.base/catch-fork-static.exp b/gdb/testsuite/gdb.base/catch-fork-static.exp
index b171a6d..9d50d5d 100644
--- a/gdb/testsuite/gdb.base/catch-fork-static.exp
+++ b/gdb/testsuite/gdb.base/catch-fork-static.exp
@@ -21,9 +21,7 @@
 # ld.so probes before reaching main, and ptrace flags were set then.  But a
 # static executable would just keep running and never catch the fork.
 
-# Until "catch fork" is implemented on other targets...
-#
-require {is_any_target "*-*-linux*" "*-*-openbsd*"}
+require allow_fork_tests
 
 # Reusing foll-fork.c since it's a simple forking program.
 standard_testfile foll-fork.c
diff --git a/gdb/testsuite/gdb.base/foll-fork.exp b/gdb/testsuite/gdb.base/foll-fork.exp
index 94755c6..12db516 100644
--- a/gdb/testsuite/gdb.base/foll-fork.exp
+++ b/gdb/testsuite/gdb.base/foll-fork.exp
@@ -17,6 +17,8 @@
 # enabled as it will be redirected to the log.
 require !gdb_debug_enabled
 
+require allow_fork_tests
+
 standard_testfile
 
 if {[build_executable "failed to prepare" $testfile $srcfile debug]} {
diff --git a/gdb/testsuite/gdb.base/foll-vfork.exp b/gdb/testsuite/gdb.base/foll-vfork.exp
index 266df46..6ca7711 100644
--- a/gdb/testsuite/gdb.base/foll-vfork.exp
+++ b/gdb/testsuite/gdb.base/foll-vfork.exp
@@ -18,12 +18,7 @@
 # either execs or exits --- since those events take somewhat different
 # code paths in GDB, both variants are exercised.
 
-# Until "set follow-fork-mode" and "catch vfork" are implemented on
-# other targets...
-#
-if {![istarget "*-linux*"]} {
-    continue
-}
+require allow_fork_tests
 
 standard_testfile .c -exit.c vforked-prog.c
 
diff --git a/gdb/testsuite/gdb.base/fork-no-detach-follow-child-dlopen.exp b/gdb/testsuite/gdb.base/fork-no-detach-follow-child-dlopen.exp
index 311d7ba..2d47d5d 100644
--- a/gdb/testsuite/gdb.base/fork-no-detach-follow-child-dlopen.exp
+++ b/gdb/testsuite/gdb.base/fork-no-detach-follow-child-dlopen.exp
@@ -23,6 +23,7 @@
 # in the source of the shlib, and "list" should display the source where
 # the program stopped.
 
+require allow_fork_tests
 require allow_shlib_tests
 
 standard_testfile .c -shlib.c
diff --git a/gdb/testsuite/gdb.base/fork-print-inferior-events.exp b/gdb/testsuite/gdb.base/fork-print-inferior-events.exp
index 26ed2f9..19ace00 100644
--- a/gdb/testsuite/gdb.base/fork-print-inferior-events.exp
+++ b/gdb/testsuite/gdb.base/fork-print-inferior-events.exp
@@ -19,6 +19,8 @@
 # inferior-events [on,off]', 'set follow-fork-mode [child,parent]' and
 # 'set detach-on-fork [on,off]' are the correct ones.
 
+require allow_fork_tests
+
 # This test relies on "run", so it cannot run on target remote stubs.
 require !use_gdb_stub
 
diff --git a/gdb/testsuite/gdb.base/fork-running-state.exp b/gdb/testsuite/gdb.base/fork-running-state.exp
index 4b810a6..c446800 100644
--- a/gdb/testsuite/gdb.base/fork-running-state.exp
+++ b/gdb/testsuite/gdb.base/fork-running-state.exp
@@ -17,6 +17,8 @@
 # in non-stop).  GDB used to miss updating the parent/child running
 # states after a fork.
 
+require allow_fork_tests
+
 standard_testfile
 
 # The test proper.
diff --git a/gdb/testsuite/gdb.base/inferior-died.exp b/gdb/testsuite/gdb.base/inferior-died.exp
index 3992561..764a88d 100644
--- a/gdb/testsuite/gdb.base/inferior-died.exp
+++ b/gdb/testsuite/gdb.base/inferior-died.exp
@@ -13,10 +13,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-# Until "set follow-fork-mode" and "catch fork" are implemented on
-# other targets...
-#
-require {istarget "*-*-linux*"}
+require allow_fork_tests
 
 require support_displaced_stepping
 
diff --git a/gdb/testsuite/gdb.base/interrupt-daemon.exp b/gdb/testsuite/gdb.base/interrupt-daemon.exp
index 161f854..8b8c61d 100644
--- a/gdb/testsuite/gdb.base/interrupt-daemon.exp
+++ b/gdb/testsuite/gdb.base/interrupt-daemon.exp
@@ -16,6 +16,8 @@
 # Make sure that we can interrupt an inferior that forks and moves to
 # its own session.
 
+require allow_fork_tests
+
 standard_testfile
 
 if {[build_executable "failed to build" $testfile $srcfile {debug}]} {
diff --git a/gdb/testsuite/gdb.base/jit-elf-fork.exp b/gdb/testsuite/gdb.base/jit-elf-fork.exp
index 81d3350..c1fa428 100644
--- a/gdb/testsuite/gdb.base/jit-elf-fork.exp
+++ b/gdb/testsuite/gdb.base/jit-elf-fork.exp
@@ -15,6 +15,7 @@
 
 # Test fork handling of an inferior that has JIT-ed objfiles.
 
+require allow_fork_tests
 require allow_shlib_tests
 
 load_lib jit-elf-helpers.exp
diff --git a/gdb/testsuite/gdb.base/multi-forks.exp b/gdb/testsuite/gdb.base/multi-forks.exp
index 61a240f..3facccb 100644
--- a/gdb/testsuite/gdb.base/multi-forks.exp
+++ b/gdb/testsuite/gdb.base/multi-forks.exp
@@ -13,11 +13,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-# Until "set follow-fork-mode" and "catch fork" are implemented on
-# other targets...
-#
-require {istarget "*-*-linux*"}
-
+require allow_fork_tests
 
 standard_testfile .c
 
diff --git a/gdb/testsuite/gdb.base/pie-fork.exp b/gdb/testsuite/gdb.base/pie-fork.exp
index 48c01d9..86407b4 100644
--- a/gdb/testsuite/gdb.base/pie-fork.exp
+++ b/gdb/testsuite/gdb.base/pie-fork.exp
@@ -16,6 +16,8 @@
 # Test that we can follow forks properly when the executable is
 # position-independent.
 
+require allow_fork_tests
+
 standard_testfile
 
 set opts [list debug pie]
diff --git a/gdb/testsuite/gdb.base/step-over-exit.exp b/gdb/testsuite/gdb.base/step-over-exit.exp
index 2370f97..6dfa7bb 100644
--- a/gdb/testsuite/gdb.base/step-over-exit.exp
+++ b/gdb/testsuite/gdb.base/step-over-exit.exp
@@ -13,11 +13,14 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-standard_testfile
-
 # Test a thread is doing step-over a syscall instruction which is exit,
 # and GDBserver should cleanup its state of step-over properly.
 
+# The testcase relies on follow-fork-mode child.
+require allow_fork_tests
+
+standard_testfile
+
 set syscall_insn ""
 
 # Define the syscall instruction for each target.
diff --git a/gdb/testsuite/gdb.base/vfork-follow-parent.exp b/gdb/testsuite/gdb.base/vfork-follow-parent.exp
index fca2993..8cb785d 100644
--- a/gdb/testsuite/gdb.base/vfork-follow-parent.exp
+++ b/gdb/testsuite/gdb.base/vfork-follow-parent.exp
@@ -19,6 +19,8 @@
 # schedule-multiple on" or "set detach-on-fork on".  Test these two resolution
 # methods.
 
+require allow_fork_tests
+
 standard_testfile .c vforked-prog.c
 
 set binfile ${testfile}-exit
diff --git a/gdb/testsuite/gdb.base/watch-before-fork.exp b/gdb/testsuite/gdb.base/watch-before-fork.exp
index 074cfbd..509561e 100644
--- a/gdb/testsuite/gdb.base/watch-before-fork.exp
+++ b/gdb/testsuite/gdb.base/watch-before-fork.exp
@@ -20,6 +20,8 @@
 # This test uses "awatch".
 require allow_hw_watchpoint_access_tests
 
+require allow_fork_tests
+
 standard_testfile
 
 if {[build_executable "failed to prepare" $testfile $srcfile debug]} {
diff --git a/gdb/testsuite/gdb.base/watch-vfork.exp b/gdb/testsuite/gdb.base/watch-vfork.exp
index 1bc61bc..503727d 100644
--- a/gdb/testsuite/gdb.base/watch-vfork.exp
+++ b/gdb/testsuite/gdb.base/watch-vfork.exp
@@ -17,6 +17,8 @@
 
 standard_testfile .c
 
+require allow_fork_tests
+
 if { [build_executable ${testfile}.exp ${testfile} $srcfile {debug}] } {
     untested "failed to compile"
     return -1
diff --git a/gdb/testsuite/gdb.multi/watchpoint-multi-exit.exp b/gdb/testsuite/gdb.multi/watchpoint-multi-exit.exp
index 70c3da9..3446296 100644
--- a/gdb/testsuite/gdb.multi/watchpoint-multi-exit.exp
+++ b/gdb/testsuite/gdb.multi/watchpoint-multi-exit.exp
@@ -17,6 +17,8 @@
 # watchpoints don't end up with stale locations, preventing resumption
 # of other inferiors.
 
+require allow_fork_tests
+
 standard_testfile
 
 if {[build_executable "failed to build" $testfile $srcfile {debug}]} {
diff --git a/gdb/testsuite/gdb.threads/foll-fork-other-thread.exp b/gdb/testsuite/gdb.threads/foll-fork-other-thread.exp
index 5245988..8ab540c 100644
--- a/gdb/testsuite/gdb.threads/foll-fork-other-thread.exp
+++ b/gdb/testsuite/gdb.threads/foll-fork-other-thread.exp
@@ -17,6 +17,8 @@
 # another thread, in different combinations of "set follow-fork
 # parent/child", and other execution modes.
 
+require allow_fork_tests
+
 standard_testfile
 
 # Line where to stop the main thread.
diff --git a/gdb/testsuite/gdb.threads/fork-child-threads.exp b/gdb/testsuite/gdb.threads/fork-child-threads.exp
index abe9769..ba9dfc2 100644
--- a/gdb/testsuite/gdb.threads/fork-child-threads.exp
+++ b/gdb/testsuite/gdb.threads/fork-child-threads.exp
@@ -13,10 +13,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-# Only GNU/Linux is known to support `set follow-fork-mode child'.
-if { ! [istarget "*-*-linux*"] } {
-    return 0
-}
+require allow_fork_tests
 
 standard_testfile
 
diff --git a/gdb/testsuite/gdb.threads/fork-plus-threads.exp b/gdb/testsuite/gdb.threads/fork-plus-threads.exp
index 3a5e66a..4ce88d3 100644
--- a/gdb/testsuite/gdb.threads/fork-plus-threads.exp
+++ b/gdb/testsuite/gdb.threads/fork-plus-threads.exp
@@ -20,6 +20,8 @@
 #
 # See https://sourceware.org/bugzilla/show_bug.cgi?id=18600
 
+require allow_fork_tests
+
 # In remote mode, we cannot continue debugging after all
 # inferiors have terminated, and this test requires that.
 if { [target_info exists gdb_protocol]
diff --git a/gdb/testsuite/gdb.threads/fork-thread-pending.exp b/gdb/testsuite/gdb.threads/fork-thread-pending.exp
index d0a1ca1..538e1ca 100644
--- a/gdb/testsuite/gdb.threads/fork-thread-pending.exp
+++ b/gdb/testsuite/gdb.threads/fork-thread-pending.exp
@@ -13,11 +13,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-# Only GNU/Linux is known to support `set follow-fork-mode child'.
-#
-if { ! [istarget "*-*-linux*"] } {
-    return 0
-}
+require allow_fork_tests
 
 standard_testfile
 
diff --git a/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.exp b/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.exp
index 1f76898..c668a65 100644
--- a/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.exp
+++ b/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.exp
@@ -16,6 +16,8 @@
 # This test verifies that several threads forking while another thread
 # is constantly stepping over a breakpoint is properly handled.
 
+require allow_fork_tests
+
 standard_testfile
 
 set linenum [gdb_get_line_number "set break here"]
diff --git a/gdb/testsuite/gdb.threads/next-fork-exec-other-thread.exp b/gdb/testsuite/gdb.threads/next-fork-exec-other-thread.exp
index bd81438..3a97127 100644
--- a/gdb/testsuite/gdb.threads/next-fork-exec-other-thread.exp
+++ b/gdb/testsuite/gdb.threads/next-fork-exec-other-thread.exp
@@ -25,6 +25,8 @@
 # 20.04.5 LTS with 32-bit kernel + 32-bit userland.  It was NOT reproducible
 # using a circa 2023 Raspberry Pi OS w/ 64-bit kernel and 32-bit userland.
 
+require allow_fork_tests
+
 standard_testfile
 
 # Line where to stop the main thread.
diff --git a/gdb/testsuite/gdb.threads/next-fork-other-thread.exp b/gdb/testsuite/gdb.threads/next-fork-other-thread.exp
index 183fda6..1cd6685 100644
--- a/gdb/testsuite/gdb.threads/next-fork-other-thread.exp
+++ b/gdb/testsuite/gdb.threads/next-fork-other-thread.exp
@@ -16,6 +16,8 @@
 # Test doing a "next" on a thread during which forks or vforks happen in other
 # threads.
 
+require allow_fork_tests
+
 standard_testfile
 
 # Line where to stop the main thread.
diff --git a/gdb/testsuite/gdb.threads/pending-fork-event-detach-ns.exp b/gdb/testsuite/gdb.threads/pending-fork-event-detach-ns.exp
index e6e311e..29a011e 100644
--- a/gdb/testsuite/gdb.threads/pending-fork-event-detach-ns.exp
+++ b/gdb/testsuite/gdb.threads/pending-fork-event-detach-ns.exp
@@ -29,6 +29,8 @@
 #     parent thread from waitpid'ing it, preventing the main thread from joining
 #     it, prevent it from writing the flag file, failing the test.
 
+require allow_fork_tests
+
 standard_testfile
 
 if { [is_remote target] } {
diff --git a/gdb/testsuite/gdb.threads/pending-fork-event-detach.exp b/gdb/testsuite/gdb.threads/pending-fork-event-detach.exp
index 8e77ab0..e627241 100644
--- a/gdb/testsuite/gdb.threads/pending-fork-event-detach.exp
+++ b/gdb/testsuite/gdb.threads/pending-fork-event-detach.exp
@@ -34,6 +34,8 @@
 # event, and erroneously create a new inferior for it.  Once fixed, the child
 # process' thread is hidden by whoever holds the pending fork event.
 
+require allow_fork_tests
+
 standard_testfile .c -touch-file.c
 
 set touch_file_bin $binfile-touch-file
diff --git a/gdb/testsuite/gdb.threads/vfork-follow-child-exec.exp b/gdb/testsuite/gdb.threads/vfork-follow-child-exec.exp
index e23db0a..0b95a75 100644
--- a/gdb/testsuite/gdb.threads/vfork-follow-child-exec.exp
+++ b/gdb/testsuite/gdb.threads/vfork-follow-child-exec.exp
@@ -16,6 +16,8 @@
 # Test following a vfork child that execs, when the vfork parent is a
 # threaded program, and it's a non-main thread that vforks.
 
+require allow_fork_tests
+
 standard_testfile
 
 if {[build_executable "failed to prepare" $testfile $srcfile {debug pthreads}]} {
diff --git a/gdb/testsuite/gdb.threads/vfork-follow-child-exit.exp b/gdb/testsuite/gdb.threads/vfork-follow-child-exit.exp
index a6b7f49..ced52df 100644
--- a/gdb/testsuite/gdb.threads/vfork-follow-child-exit.exp
+++ b/gdb/testsuite/gdb.threads/vfork-follow-child-exit.exp
@@ -16,6 +16,8 @@
 # Test following a vfork child that exits, when the vfork parent is a
 # threaded program, and it's a non-main thread that vforks.
 
+require allow_fork_tests
+
 standard_testfile
 
 if {[build_executable "failed to prepare" $testfile $srcfile {debug pthreads}]} {
diff --git a/gdb/testsuite/gdb.threads/vfork-multi-inferior.exp b/gdb/testsuite/gdb.threads/vfork-multi-inferior.exp
index fd081b3..d552039 100644
--- a/gdb/testsuite/gdb.threads/vfork-multi-inferior.exp
+++ b/gdb/testsuite/gdb.threads/vfork-multi-inferior.exp
@@ -25,6 +25,8 @@
 # To catch the bug, this test verifies that we can hit a breakpoint after a
 # vfork call, while a second inferior runs in the background.
 
+require allow_fork_tests
+
 require !use_gdb_stub
 
 standard_testfile .c -sleep.c
diff --git a/gdb/testsuite/gdb.threads/vfork-multi-thread.exp b/gdb/testsuite/gdb.threads/vfork-multi-thread.exp
index 2b9294d..61811ae 100644
--- a/gdb/testsuite/gdb.threads/vfork-multi-thread.exp
+++ b/gdb/testsuite/gdb.threads/vfork-multi-thread.exp
@@ -30,6 +30,8 @@
 # breakpoints are removed, so the main thread would miss the breakpoint and run
 # until exit.
 
+require allow_fork_tests
+
 standard_testfile
 
 if { [build_executable "failed to prepare" ${testfile} ${srcfile} {debug pthreads}] } {
diff --git a/gdb/testsuite/gdb.threads/watchpoint-fork.exp b/gdb/testsuite/gdb.threads/watchpoint-fork.exp
index 376ca2a..8e9b1c3 100644
--- a/gdb/testsuite/gdb.threads/watchpoint-fork.exp
+++ b/gdb/testsuite/gdb.threads/watchpoint-fork.exp
@@ -21,6 +21,8 @@
 # must be done before starting the test so as to not disrupt the execution
 # of the actual test.
 
+require allow_fork_tests
+
 set allow_hw_watchpoint_tests_p [allow_hw_watchpoint_tests]
 
 set testfile watchpoint-fork