[PATCH] gdb/testsuite: allow "require" callbacks to provide a reason

[Simon Marchi <simon.marchi@efficios.com>]

When an allow_* proc returns false, it can be a bit difficult what check
failed exactly, if the procedure does multiple checks.  To make
investigation easier, I propose to allow the "require" callbacks to be
able to return a list of two elements: the zero/non-zero value, and a
reason string.

Use the new feature in allow_hipcc_tests to demonstrate it (it's also
where I hit actually hit this inconvenience).  On my computer (where GDB
is built with amd-dbgapi support but where I don't have a suitable GPU
target), I get:

    UNSUPPORTED: gdb.rocm/simple.exp: require failed: allow_hipcc_tests (no suitable amdgpu targets found)

vs before:

    UNSUPPORTED: gdb.rocm/simple.exp: require failed: allow_hipcc_tests

Change-Id: Id1966535b87acfcbe9eac99f49dc1196398c6578
---
 gdb/testsuite/lib/gdb.exp  | 37 +++++++++++++++++++++++++++++--------
 gdb/testsuite/lib/rocm.exp |  8 ++++----
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 46aa1441d6d0..7fb4f1cbdab4 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -9251,22 +9251,43 @@ gdb_caching_proc have_avx {} {
 #
 # ARG can either be a name, or of the form !NAME.
 #
-# Each name is a proc to evaluate in the caller's context.  It returns
-# a boolean, and a "!" means to invert the result.  If this is
-# nonzero, all is well.  If it is zero, an "untested" is emitted and
-# this proc causes the caller to return.
+# Each name is a proc to evaluate in the caller's context.  It can return a
+# boolean or a two element list with a boolean and a reason string.
+# A "!" means to invert the result.  If this is true, all is well.  If it is
+# false, an "unsupported" is emitted and this proc causes the caller to return.
+#
+# The reason string is used to provide some context about a require failure,
+# and is included in the "unsupported" message.
 
 proc require { args } {
     foreach arg $args {
 	if {[string index $arg 0] == "!"} {
-	    set ok 0
+	    set required_val 0
 	    set fn [string range $arg 1 end]
 	} else {
-	    set ok 1
+	    set required_val 1
 	    set fn $arg
 	}
-	if {$ok != !![uplevel 1 $fn]} {
-	    unsupported "require failed: $arg"
+
+	set result [uplevel 1 $fn]
+	set len [llength $result]
+	if { $len == 2 } {
+	    set actual_val [lindex $result 0]
+	    set msg [lindex $result 1]
+	} elseif { $len == 1 } {
+	    set actual_val $result
+	    set msg ""
+	} else {
+	    error "proc $fn returned a list of unexpected length $len"
+	}
+
+	if {$required_val != !!$actual_val} {
+	    if { [string length $msg] > 0 } {
+		unsupported "require failed: $arg ($msg)"
+	    } else {
+		unsupported "require failed: $arg"
+	    }
+
 	    return -code return 0
 	}
     }
diff --git a/gdb/testsuite/lib/rocm.exp b/gdb/testsuite/lib/rocm.exp
index b3e435339dbc..389d73bcaa5f 100644
--- a/gdb/testsuite/lib/rocm.exp
+++ b/gdb/testsuite/lib/rocm.exp
@@ -64,19 +64,19 @@ gdb_caching_proc allow_hipcc_tests {} {
     # testing against GDBserver, there's no point in running the ROCm
     # tests.
     if {[target_info gdb_protocol] != ""} {
-	return 0
+	return {0 "remote debugging"}
     }
 
     # Ensure that GDB is built with amd-dbgapi support.
     set output [remote_exec host $::GDB "$::INTERNAL_GDBFLAGS --configuration"]
     if { [string first "--with-amd-dbgapi" $output] == -1 } {
-	return 0
+	return {0 "amd-dbgapi not supported"}
     }
 
     # Check we have a working hipcc compiler available.
     set targets [hcc_amdgpu_targets]
     if { [llength $targets] == 0} {
-	return 0
+	return {0 "no suitable amdgpu targets found"}
     }
 
     set flags [list hip additional_flags=--offload-arch=[join $targets ","]]
@@ -93,7 +93,7 @@ gdb_caching_proc allow_hipcc_tests {} {
 		return 0;
 	    }
 	} executable $flags]} {
-	return 0
+	return {0 "failed to compile hip program"}
     }
 
     return 1
-- 
2.40.0