[PATCH 1/2] [gdb] Make regformats/regdat.sh shellcheck-clean

[Tom de Vries <tdevries@suse.de>]

Make regformats/regdat.sh shellcheck-clean:
- use read -r
- use $()
- ignore intentional word-splitting
- add missing quotes
- use $(())

Handle a shellcheck error in this:
...
  if eval test \"\${${r}}\" = \"\ \"
...
by simplifying to:
...
  eval "rvalue=\$$r"
  if test "${rvalue:-}" = " "
...

Note that shellcheck can't detect that rvalue is assigned to, so we use
'${parameter:-word}' to use default value "", to silence a SC2154 [1].

Also, handle a shellcheck error in this:
...
  eval ${r}=""
...
by simplifying to:
...
  eval "$r=''"
...

Tested on x86_64-linux using:
...
$ for f in $(find gdb/regformats -name "*.dat"); do \
      sh gdb/regformats/regdat.sh \
          $f \
	  gdbsupport/osabi.def \
	  $(echo $f | sed 's%/%-%g'); \
  done
...
and comparing the generated files with and without this patch.

[1] https://www.shellcheck.net/wiki/SC2154
---
 gdb/contrib/shellcheck.sh |  1 -
 gdb/regformats/regdat.sh  | 25 ++++++++++++++-----------
 2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/gdb/contrib/shellcheck.sh b/gdb/contrib/shellcheck.sh
index f7f7bf9efbf..a3e80a553f4 100755
--- a/gdb/contrib/shellcheck.sh
+++ b/gdb/contrib/shellcheck.sh
@@ -47,7 +47,6 @@ for f in "$@"; do
 	    | gdb/contrib/gdb-add-index.sh \
 	    | gdb/gdb_buildall.sh \
 	    | gdb/gdb_mbuild.sh \
-	    | gdb/regformats/regdat.sh \
 	    | gdb/testsuite/lib/pdtrace.in)
 	    # Skip unclean files.
 	    continue
diff --git a/gdb/regformats/regdat.sh b/gdb/regformats/regdat.sh
index b57b76132aa..01f2dabe459 100755
--- a/gdb/regformats/regdat.sh
+++ b/gdb/regformats/regdat.sh
@@ -25,7 +25,7 @@ do_read ()
 {
     type=""
     entry=""
-    while read line
+    while read -r line
     do
 	if test "${line}" = ""
 	then
@@ -42,9 +42,11 @@ ${line}"
 	    # The semantics of IFS varies between different SH's.  Some
 	    # treat ``::' as three fields while some treat it as just too.
 	    # Work around this by eliminating ``::'' ....
-	    line="`echo "${line}" | sed -e 's/::/: :/g' -e 's/::/: :/g'`"
+	    line="$(echo "${line}" | sed -e 's/::/: :/g' -e 's/::/: :/g')"
 
 	    OFS="${IFS}" ; IFS="[:]"
+	    # Word-splitting on read variable is required.
+	    # shellcheck disable=SC2086
 	    eval read ${read} <<EOF
 ${line}
 EOF
@@ -54,9 +56,10 @@ EOF
 	    # that ended up with just that space character.
 	    for r in ${read}
 	    do
-		if eval test \"\${${r}}\" = \"\ \"
+		eval "rvalue=\$$r"
+		if test "${rvalue:-}" = " "
 		then
-		    eval ${r}=""
+		    eval "$r=''"
 		fi
 	    done
 
@@ -71,7 +74,7 @@ EOF
     fi
 }
 
-if test ! -r $1; then
+if test ! -r "$1"; then
   echo "$0: Could not open $1." 1>&2
   exit 1
 fi
@@ -105,8 +108,8 @@ EOF
 }
 
 
-exec > new-$3
-copyright $1
+exec > new-"$3"
+copyright "$1"
 echo '#include "regdef.h"'
 echo '#include "tdesc.h"'
 echo
@@ -119,7 +122,7 @@ xmlosabi=x
 expedite=x
 feature=x
 osabi=unknown
-exec < $1
+exec < "$1"
 while do_read
 do
   if test "${type}" = "name"; then
@@ -162,13 +165,13 @@ do
     echo "  tdesc_create_reg (feature, \"${entry}\","
     echo "  0, 0, NULL, ${type}, NULL);"
 
-    offset=`expr ${offset} + ${type}`
-    i=`expr $i + 1`
+    offset=$((offset + type))
+    i=$((i + 1))
   fi
 done
 
 echo
-echo "static const char *expedite_regs_${name}[] = { \"`echo ${expedite} | sed 's/,/", "/g'`\", 0 };"
+echo "static const char *expedite_regs_${name}[] = { \"$(echo "${expedite}" | sed 's/,/", "/g')\", 0 };"
 
 echo "#ifndef IN_PROCESS_AGENT"
 if test "${feature}" != x; then
-- 
2.51.0