gdb/testsuite: Fix set_unbuffered_mode.o handling in parallel mode

Cygwin/MinGW testing links in a set_unbuffered_mode.o object to all
test programs.  When running the testsuite in parallel mode, on
Cygwin, I noticed errors like:

  ERROR: remote_download to host of ..../build/set_unbuffered_mode.o to ..../build/set_unbuffered_mode_saved.o: cp: cannot open '..../build/set_unbuffered_mode.o' for reading: No such file or directory
...
  ERROR: remote_download to host of ..../build/set_unbuffered_mode.o to ..../build/set_unbuffered_mode_saved.o: cp: cannot stat '..../build/set_unbuffered_mode.o': No such file or directory
...
  ERROR: remote_download to host of ..../build/set_unbuffered_mode.o to ..../build/set_unbuffered_mode_saved.o: cp: skipping file '..../build/set_unbuffered_mode.o', as it was replaced while being copied

(Absolute paths elided above.)

The problem is that gdb_compile's unbuffered_mode_obj cache isn't
parallel safe.  This is fixed in this commit.

Reviewed-by: Kevin Buettner <kevinb@redhat.com>
Change-Id: I67a289473c14ce0603d4b0beb755b124588f18d2

diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 606a393271fc79c40fc08d21ed9d90be843905cb..d48ea37c0cc047298e51b70190b48678b32c3d59 100644 (file)
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -5569,10 +5569,20 @@ proc gdb_compile {source dest type options} {
            #  which is time consuming, especially if we're remote
            #  host testing.
            #
+           # Note the special care for GDB_PARALLEL.  In that
+           # scenario, multiple expect instances will potentially try
+           # to compile the object file at the same time.  The result
+           # should be identical for every one of them, so we just
+           # need to make sure that the final objfile is written to
+           # atomically.
+
            if { $gdb_saved_set_unbuffered_mode_obj == "" } {
                verbose "compiling gdb_saved_set_unbuffered_obj"
                set unbuf_src ${srcdir}/lib/set_unbuffered_mode.c
-               set unbuf_obj ${objdir}/set_unbuffered_mode.o
+               # This gives us a per-expect-instance unique filename,
+               # which is important for GDB_PARALLEL.  See comments
+               # above.
+               set unbuf_obj [standard_temp_file set_unbuffered_mode.o]
 
                set result [gdb_compile "${unbuf_src}" "${unbuf_obj}" object {nowarnings}]
                if { $result != "" } {
@@ -5585,7 +5595,14 @@ proc gdb_compile {source dest type options} {
                }
                # Link a copy of the output object, because the
                # original may be automatically deleted.
-               remote_download host $unbuf_obj $gdb_saved_set_unbuffered_mode_obj
+               if {[info exists ::GDB_PARALLEL]} {
+                   # Make sure to write the .o file atomically.
+                   # (Note GDB_PARALLEL mode does not support remote
+                   # host testing.)
+                   file rename -force -- $unbuf_obj $gdb_saved_set_unbuffered_mode_obj
+               } else {
+                   remote_download host $unbuf_obj $gdb_saved_set_unbuffered_mode_obj
+               }
            } else {
                verbose "gdb_saved_set_unbuffered_obj already compiled"
            }