[binutils-gdb] gdb: fix shellcheck warnings SC2154 (referenced but not assigned) in gdbarch.sh

[gdb-buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 1207375d768ae2b901c3bea6543b610c461160dd ***

commit 1207375d768ae2b901c3bea6543b610c461160dd
Author:     Simon Marchi <simon.marchi@efficios.com>
AuthorDate: Wed Apr 29 20:35:35 2020 -0400
Commit:     Simon Marchi <simon.marchi@efficios.com>
CommitDate: Wed Apr 29 20:35:35 2020 -0400

    gdb: fix shellcheck warnings SC2154 (referenced but not assigned) in gdbarch.sh
    
    Fix all instances of this kind of warning:
    
        In gdbarch.sh line 96:
                        m ) staticdefault="${predefault}" ;;
                                           ^-----------^ SC2154: predefault is referenced but not assigned.
    
    These warnings appear because we are doing something a bit funky when reading
    the gdbarch fields.  These variables are not assigned explicitly, but
    using some `eval` commands.
    
    I don't think there is so much we can fix about those warnings.  To
    silence them, I've changed `${foo}` to `${foo:-}`.  This tells the shell
    to substitute with an empty string if `foo` is not defined.  This
    retains the current behavior, but the warnings go away.
    
    gdb/ChangeLog:
    
            * gdbarch.sh: Use ${foo:-} where shellcheck would report a
            "referenced but not assigned" warning.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index dee9a6edd3..eb6841640b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2020-04-29  Simon Marchi  <simon.marchi@efficios.com>
+
+	* gdbarch.sh: Use ${foo:-} where shellcheck would report a
+	"referenced but not assigned" warning.
+
 2020-04-29  Simon Marchi  <simon.marchi@efficios.com>
 
 	* gdbarch.sh: Remove code that sets fallbackdefault.
diff --git a/gdb/gdbarch.sh b/gdb/gdbarch.sh
index 4e4cc827b8..24f8cdfe90 100755
--- a/gdb/gdbarch.sh
+++ b/gdb/gdbarch.sh
@@ -75,7 +75,7 @@ ${line}
 EOF
 	    IFS="${OFS}"
 
-	    if test -n "${garbage_at_eol}"
+	    if test -n "${garbage_at_eol:-}"
 	    then
 		echo "Garbage at end-of-line in ${line}" 1>&2
 		kill $$
@@ -93,19 +93,19 @@ EOF
 	    done
 
 	    case "${class}" in
-		m ) staticdefault="${predefault}" ;;
+		m ) staticdefault="${predefault:-}" ;;
 		M ) staticdefault="0" ;;
 		* ) test "${staticdefault}" || staticdefault=0 ;;
 	    esac
 
 	    case "${class}" in
 	    F | V | M )
-		case "${invalid_p}" in
+		case "${invalid_p:-}" in
 		"" )
 		    if test -n "${predefault}"
 		    then
 			#invalid_p="gdbarch->${function} == ${predefault}"
-			predicate="gdbarch->${function} != ${predefault}"
+			predicate="gdbarch->${function:-} != ${predefault}"
 		    elif class_is_variable_p
 		    then
 			predicate="gdbarch->${function} != 0"
@@ -139,7 +139,7 @@ EOF
 
 fallback_default_p ()
 {
-    { [ -n "${postdefault}" ] && [ "x${invalid_p}" != "x0" ]; } \
+    { [ -n "${postdefault:-}" ] && [ "x${invalid_p}" != "x0" ]; } \
 	|| { [ -n "${predefault}" ] && [ "x${invalid_p}" = "x0" ]; }
 }
 
@@ -1206,7 +1206,7 @@ exec > new-gdbarch.log
 function_list | while do_read
 do
     cat <<EOF
-${class} ${returntype} ${function} ($formal)
+${class} ${returntype:-} ${function} (${formal:-})
 EOF
     for r in ${read}
     do
@@ -2119,7 +2119,7 @@ do
 	fi
 	printf "  if (gdbarch_debug >= 2)\n"
 	printf "    fprintf_unfiltered (gdb_stdlog, \"gdbarch_%s called\\\\n\");\n" "$function"
-	if [ "x${actual}" = "x-" ] || [ "x${actual}" = "x" ]
+	if [ "x${actual:-}" = "x-" ] || [ "x${actual:-}" = "x" ]
 	then
 	    if class_is_multiarch_p
 	    then