diff mbox

configure: Use $(..) instead of deprecated `..`

Message ID 1463404220-5945-1-git-send-email-sw@weilnetz.de
State New
Headers show

Commit Message

Stefan Weil May 16, 2016, 1:10 p.m. UTC 
This fixes these warnings from shellcheck:

    ^-- SC2006: Use $(..) instead of deprecated `..`

Signed-off-by: Stefan Weil <sw@weilnetz.de>
---

More warnings from shellcheck for configure and other files
will be handled by later patches.

Setting CONFIG_STAMP below needed special care.

Regards
Stefan W.


 configure | 174 +++++++++++++++++++++++++++++++-------------------------------
 1 file changed, 87 insertions(+), 87 deletions(-)

Comments

Michael Tokarev May 29, 2016, 8:19 a.m. UTC | #1 
Applied to -trivial, thanks!

/mjt
Maciej W. Rozycki June 8, 2016, 12:16 p.m. UTC | #2 
On Mon, 16 May 2016, Stefan Weil wrote:

> This fixes these warnings from shellcheck:
> 
>     ^-- SC2006: Use $(..) instead of deprecated `..`
> 
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> ---
> 
> More warnings from shellcheck for configure and other files
> will be handled by later patches.

 Unlike `..` the $(..) Bourne shell construct is not fully portable, some 
implementations do not recognise it.  Consequently this change potentially 
breaks building QEMU on some systems, possibly in a non-obvious way, as 
there's no explicit check for the presence this feature and a graceful 
failure path included with this patch or the other one AFAICT.  We may or 
may not care about those systems, but still this is a functional 
regression and therefore I think there has to be a good reason for 
introducing it.

 So what's the technical justification -- beyond shutting up some random 
checker tool -- for making this change?  Does the benefit recognised in 
making this change outweigh the limitation introduced?  How about handling 
failures properly?

 NB given the above, and especially because of the introduced functional 
regression mentioned, I don't think this change qualifies as trivial.

  Maciej
Daniel P. Berrangé June 8, 2016, 12:48 p.m. UTC | #3 
On Wed, Jun 08, 2016 at 01:16:59PM +0100, Maciej W. Rozycki wrote:
> On Mon, 16 May 2016, Stefan Weil wrote:
> 
> > This fixes these warnings from shellcheck:
> > 
> >     ^-- SC2006: Use $(..) instead of deprecated `..`
> > 
> > Signed-off-by: Stefan Weil <sw@weilnetz.de>
> > ---
> > 
> > More warnings from shellcheck for configure and other files
> > will be handled by later patches.
> 
>  Unlike `..` the $(..) Bourne shell construct is not fully portable, some 
> implementations do not recognise it.  Consequently this change potentially 
> breaks building QEMU on some systems, possibly in a non-obvious way, as 
> there's no explicit check for the presence this feature and a graceful 
> failure path included with this patch or the other one AFAICT.  We may or 
> may not care about those systems, but still this is a functional 
> regression and therefore I think there has to be a good reason for 
> introducing it.

I found that the bash wiki has a note about this

  http://wiki.bash-hackers.org/scripting/obsolete

  "This is the older Bourne-compatible form of the command substitution.
   Both the `COMMANDS` and $(COMMANDS) syntaxes are specified by POSIX,
   but the latter is _greatly_ preferred, though the former is unfortunately
   still very prevalent in scripts. New-style command substitutions are
   widely implemented by every modern shell (and then some). The only
   reason for using backticks is for compatibility with a real Bourne
   shell (like Heirloom). Backtick command substitutions require special
   escaping when nested, and examples found in the wild are improperly
   quoted more often than not."

>  So what's the technical justification -- beyond shutting up some random 
> checker tool -- for making this change?  Does the benefit recognised in 
> making this change outweigh the limitation introduced?  How about handling 
> failures properly?

Seems the main benefit of $(...) is around escaping/quoting. Since `..`
is in POSIX and widely used, support for it is never going to be deleted,
regardless of whether people decide to call it 'deprecated'. IOW, unless
QEMU hits the issue with the escaping/quoting, there's no compelling reason
to avoid `...`

Regards,
Daniel
Stefan Weil June 8, 2016, 1:07 p.m. UTC | #4 
Am 08.06.2016 um 14:16 schrieb Maciej W. Rozycki:
> On Mon, 16 May 2016, Stefan Weil wrote:
> 
>> This fixes these warnings from shellcheck:
>>
>>     ^-- SC2006: Use $(..) instead of deprecated `..`
>>
>> Signed-off-by: Stefan Weil <sw@weilnetz.de>
>> ---
>>
>> More warnings from shellcheck for configure and other files
>> will be handled by later patches.
> 
>  Unlike `..` the $(..) Bourne shell construct is not fully portable, some 
> implementations do not recognise it.  Consequently this change potentially 
> breaks building QEMU on some systems, possibly in a non-obvious way, as 
> there's no explicit check for the presence this feature and a graceful 
> failure path included with this patch or the other one AFAICT.  We may or 
> may not care about those systems, but still this is a functional 
> regression and therefore I think there has to be a good reason for 
> introducing it.


As the $() construct was already used in QEMU code before this commit
(we had a mixture of both styles), I don't expect anything to break
which was not broken before.

Stefan
Maciej W. Rozycki June 8, 2016, 1:46 p.m. UTC | #5 
On Wed, 8 Jun 2016, Stefan Weil wrote:

> >  Unlike `..` the $(..) Bourne shell construct is not fully portable, some 
> > implementations do not recognise it.  Consequently this change potentially 
> > breaks building QEMU on some systems, possibly in a non-obvious way, as 
> > there's no explicit check for the presence this feature and a graceful 
> > failure path included with this patch or the other one AFAICT.  We may or 
> > may not care about those systems, but still this is a functional 
> > regression and therefore I think there has to be a good reason for 
> > introducing it.
> 
> 
> As the $() construct was already used in QEMU code before this commit
> (we had a mixture of both styles), I don't expect anything to break
> which was not broken before.

 Fair enough then.  Thanks for the explanation.  It would have made sense 
to mention it in the commit message though.

  Maciej
Eric Blake June 8, 2016, 2:05 p.m. UTC | #6 
On 06/08/2016 06:16 AM, Maciej W. Rozycki wrote:
> On Mon, 16 May 2016, Stefan Weil wrote:
> 
>> This fixes these warnings from shellcheck:
>>
>>     ^-- SC2006: Use $(..) instead of deprecated `..`
>>
>> Signed-off-by: Stefan Weil <sw@weilnetz.de>
>> ---
>>
>> More warnings from shellcheck for configure and other files
>> will be handled by later patches.
> 
>  Unlike `..` the $(..) Bourne shell construct is not fully portable, some 
> implementations do not recognise it.

All POSIX implementations support it. The only shell that doesn't is
from Solaris /bin/sh, and that pre-dates modern OpenSolaris which has
(finally) modernized their shell.  And I don't think we have anyone
actively trying to build qemu for Solaris (we have bug reports for
mingw, BSD, and Mac OS, but I haven't seen anyone complaining about a
failed Solaris build).

>  So what's the technical justification -- beyond shutting up some random 
> checker tool -- for making this change?  Does the benefit recognised in 
> making this change outweigh the limitation introduced?  How about handling 
> failures properly?

We already have places where we assume a POSIX shell, and $() is cleaner
to use than `` when it comes to nesting quotes.

>  NB given the above, and especially because of the introduced functional 
> regression mentioned, I don't think this change qualifies as trivial.

I agree that calling this trivial may be a stretch, but I see no problem
with the patch itself if the commit message is beefed up to provide more
justification than just "silence a lint-like tool".
Maciej W. Rozycki June 8, 2016, 2:38 p.m. UTC | #7 
On Wed, 8 Jun 2016, Eric Blake wrote:

> >  Unlike `..` the $(..) Bourne shell construct is not fully portable, some 
> > implementations do not recognise it.
> 
> All POSIX implementations support it. The only shell that doesn't is
> from Solaris /bin/sh, and that pre-dates modern OpenSolaris which has
> (finally) modernized their shell.  And I don't think we have anyone
> actively trying to build qemu for Solaris (we have bug reports for
> mingw, BSD, and Mac OS, but I haven't seen anyone complaining about a
> failed Solaris build).

 The IRIX shell doesn't support it either I believe, as I suppose some 
other older systems.  We may or may not care about them (we might as well 
kindly ask people to install bash or suchlike), but I think it makes sense 
to make it explicit.

> >  NB given the above, and especially because of the introduced functional 
> > regression mentioned, I don't think this change qualifies as trivial.
> 
> I agree that calling this trivial may be a stretch, but I see no problem
> with the patch itself if the commit message is beefed up to provide more
> justification than just "silence a lint-like tool".

 Agreed, I think it's worth the little extra time needed to write it and 
have a commit description explanatory enough for anyone to understand the 
motivation.  Having one often turns a questionable change into an obvious 
one, not to mention that someone might scratch their head staring at a 
commit years on from now as they try to understand what the author 
actually meant to do.

 I find myself doing this frequently when discovering bugs introduced to 
software 10-15 years ago with commits having little if any description (as 
per the standards of that time), trying to figure out how to fix the bug
while not breaking the original intent of the change.

  Maciej
Peter Maydell June 8, 2016, 3:07 p.m. UTC | #8 
On 8 June 2016 at 15:05, Eric Blake <eblake@redhat.com> wrote:
> On 06/08/2016 06:16 AM, Maciej W. Rozycki wrote:
>> On Mon, 16 May 2016, Stefan Weil wrote:
>>
>>> This fixes these warnings from shellcheck:
>>>
>>>     ^-- SC2006: Use $(..) instead of deprecated `..`
>>>
>>> Signed-off-by: Stefan Weil <sw@weilnetz.de>
>>> ---
>>>
>>> More warnings from shellcheck for configure and other files
>>> will be handled by later patches.
>>
>>  Unlike `..` the $(..) Bourne shell construct is not fully portable, some
>> implementations do not recognise it.
>
> All POSIX implementations support it. The only shell that doesn't is
> from Solaris /bin/sh, and that pre-dates modern OpenSolaris which has
> (finally) modernized their shell.  And I don't think we have anyone
> actively trying to build qemu for Solaris (we have bug reports for
> mingw, BSD, and Mac OS, but I haven't seen anyone complaining about a
> failed Solaris build).

We did have somebody some years back, and as I recall what
we said was roughly "this is the 21st century and we assume /bin/sh
is POSIX".

thanks
-- PMM
diff mbox

Patch

diff --git a/configure b/configure
index bbf9005..5a83345 100755
--- a/configure
+++ b/configure
@@ -164,7 +164,7 @@  have_backend () {
 }
 
 # default parameters
-source_path=`dirname "$0"`
+source_path=$(dirname "$0")
 cpu=""
 iasl="iasl"
 interp_prefix="/usr/gnemul/qemu-%M"
@@ -323,7 +323,7 @@  jemalloc="no"
 
 # parse CC options first
 for opt do
-  optarg=`expr "x$opt" : 'x[^=]*=\(.*\)'`
+  optarg=$(expr "x$opt" : 'x[^=]*=\(.*\)')
   case "$opt" in
   --cross-prefix=*) cross_prefix="$optarg"
   ;;
@@ -398,7 +398,7 @@  if test "$debug_info" = "yes"; then
 fi
 
 # make source path absolute
-source_path=`cd "$source_path"; pwd`
+source_path=$(cd "$source_path"; pwd)
 
 # running configure in the source tree?
 # we know that's the case if configure is there.
@@ -443,7 +443,7 @@  elif check_define __sun__ ; then
 elif check_define __HAIKU__ ; then
   targetos='Haiku'
 else
-  targetos=`uname -s`
+  targetos=$(uname -s)
 fi
 
 # Some host OSes need non-standard checks for which CPU to use.
@@ -461,7 +461,7 @@  Darwin)
   fi
   ;;
 SunOS)
-  # `uname -m` returns i86pc even on an x86_64 box, so default based on isainfo
+  # $(uname -m) returns i86pc even on an x86_64 box, so default based on isainfo
   if test -z "$cpu" && test "$(isainfo -k)" = "amd64"; then
     cpu="x86_64"
   fi
@@ -507,7 +507,7 @@  elif check_define __aarch64__ ; then
 elif check_define __hppa__ ; then
   cpu="hppa"
 else
-  cpu=`uname -m`
+  cpu=$(uname -m)
 fi
 
 ARCH=
@@ -627,7 +627,7 @@  SunOS)
   ld="gld"
   smbd="${SMBD-/usr/sfw/sbin/smbd}"
   needs_libsunmath="no"
-  solarisrev=`uname -r | cut -f2 -d.`
+  solarisrev=$(uname -r | cut -f2 -d.)
   if [ "$cpu" = "i386" -o "$cpu" = "x86_64" ] ; then
     if test "$solarisrev" -le 9 ; then
       if test -f /opt/SUNWspro/prod/lib/libsunmath.so.1; then
@@ -722,7 +722,7 @@  fi
 werror=""
 
 for opt do
-  optarg=`expr "x$opt" : 'x[^=]*=\(.*\)'`
+  optarg=$(expr "x$opt" : 'x[^=]*=\(.*\)')
   case "$opt" in
   --help|-h) show_help=yes
   ;;
@@ -846,9 +846,9 @@  for opt do
   ;;
   --audio-drv-list=*) audio_drv_list="$optarg"
   ;;
-  --block-drv-rw-whitelist=*|--block-drv-whitelist=*) block_drv_rw_whitelist=`echo "$optarg" | sed -e 's/,/ /g'`
+  --block-drv-rw-whitelist=*|--block-drv-whitelist=*) block_drv_rw_whitelist=$(echo "$optarg" | sed -e 's/,/ /g')
   ;;
-  --block-drv-ro-whitelist=*) block_drv_ro_whitelist=`echo "$optarg" | sed -e 's/,/ /g'`
+  --block-drv-ro-whitelist=*) block_drv_ro_whitelist=$(echo "$optarg" | sed -e 's/,/ /g')
   ;;
   --enable-debug-tcg) debug_tcg="yes"
   ;;
@@ -943,7 +943,7 @@  for opt do
   ;;
   --enable-cocoa)
       cocoa="yes" ;
-      audio_drv_list="coreaudio `echo $audio_drv_list | sed s,coreaudio,,g`"
+      audio_drv_list="coreaudio $(echo $audio_drv_list | sed s,coreaudio,,g)"
   ;;
   --disable-system) softmmu="no"
   ;;
@@ -1388,7 +1388,7 @@  fi
 
 # Consult white-list to determine whether to enable werror
 # by default.  Only enable by default for git builds
-z_version=`cut -f3 -d. $source_path/VERSION`
+z_version=$(cut -f3 -d. $source_path/VERSION)
 
 if test -z "$werror" ; then
     if test -d "$source_path/.git" -a \
@@ -1617,7 +1617,7 @@  if test "$solaris" = "yes" ; then
         "install fileutils from www.blastwave.org using pkg-get -i fileutils" \
         "to get ginstall which is used by default (which lives in /opt/csw/bin)"
   fi
-  if test "`path_of $install`" = "/usr/sbin/install" ; then
+  if test "$(path_of $install)" = "/usr/sbin/install" ; then
     error_exit "Solaris /usr/sbin/install is not an appropriate install program." \
         "try ginstall from the GNU fileutils available from www.blastwave.org" \
         "using pkg-get -i fileutils, or use --install=/usr/ucb/install"
@@ -1636,7 +1636,7 @@  fi
 if test -z "${target_list+xxx}" ; then
     target_list="$default_target_list"
 else
-    target_list=`echo "$target_list" | sed -e 's/,/ /g'`
+    target_list=$(echo "$target_list" | sed -e 's/,/ /g')
 fi
 
 # Check that we recognised the target name; this allows a more
@@ -1886,8 +1886,8 @@  if test "$seccomp" != "no" ; then
 
     if test "$libseccomp_minver" != "" &&
        $pkg_config --atleast-version=$libseccomp_minver libseccomp ; then
-        libs_softmmu="$libs_softmmu `$pkg_config --libs libseccomp`"
-        QEMU_CFLAGS="$QEMU_CFLAGS `$pkg_config --cflags libseccomp`"
+        libs_softmmu="$libs_softmmu $($pkg_config --libs libseccomp)"
+        QEMU_CFLAGS="$QEMU_CFLAGS $($pkg_config --cflags libseccomp)"
         seccomp="yes"
     else
         if test "$seccomp" = "yes" ; then
@@ -2127,8 +2127,8 @@  fi
 x11_cflags=
 x11_libs=-lX11
 if $pkg_config --exists "x11"; then
-    x11_cflags=`$pkg_config --cflags x11`
-    x11_libs=`$pkg_config --libs x11`
+    x11_cflags=$($pkg_config --cflags x11)
+    x11_libs=$($pkg_config --libs x11)
 fi
 
 ##########################################
@@ -2155,9 +2155,9 @@  if test "$gtk" != "no"; then
       gtkversion="2.18.0"
     fi
     if $pkg_config --exists "$gtkpackage >= $gtkversion"; then
-        gtk_cflags=`$pkg_config --cflags $gtkpackage`
-        gtk_libs=`$pkg_config --libs $gtkpackage`
-        gtk_version=`$pkg_config --modversion $gtkpackage`
+        gtk_cflags=$($pkg_config --cflags $gtkpackage)
+        gtk_libs=$($pkg_config --libs $gtkpackage)
+        gtk_version=$($pkg_config --modversion $gtkpackage)
         if $pkg_config --exists "$gtkx11package >= $gtkversion"; then
             gtk_cflags="$gtk_cflags $x11_cflags"
             gtk_libs="$gtk_libs $x11_libs"
@@ -2195,8 +2195,8 @@  gnutls_gcrypt=no
 gnutls_nettle=no
 if test "$gnutls" != "no"; then
     if gnutls_works; then
-        gnutls_cflags=`$pkg_config --cflags gnutls`
-        gnutls_libs=`$pkg_config --libs gnutls`
+        gnutls_cflags=$($pkg_config --cflags gnutls)
+        gnutls_libs=$($pkg_config --libs gnutls)
         libs_softmmu="$gnutls_libs $libs_softmmu"
         libs_tools="$gnutls_libs $libs_tools"
 	QEMU_CFLAGS="$QEMU_CFLAGS $gnutls_cflags"
@@ -2220,7 +2220,7 @@  if test "$gnutls" != "no"; then
 	    gnutls_gcrypt=no
 	    gnutls_nettle=yes
 	elif $pkg_config --exists 'gnutls >= 2.12'; then
-	    case `$pkg_config --libs --static gnutls` in
+	    case $($pkg_config --libs --static gnutls) in
 		*gcrypt*)
 		    gnutls_gcrypt=yes
 		    gnutls_nettle=no
@@ -2281,7 +2281,7 @@  has_libgcrypt_config() {
 
     if test -n "$cross_prefix"
     then
-	host=`libgcrypt-config --host`
+	host=$(libgcrypt-config --host)
 	if test "$host-" != $cross_prefix
 	then
 	    return 1
@@ -2293,8 +2293,8 @@  has_libgcrypt_config() {
 
 if test "$gcrypt" != "no"; then
     if has_libgcrypt_config; then
-        gcrypt_cflags=`libgcrypt-config --cflags`
-        gcrypt_libs=`libgcrypt-config --libs`
+        gcrypt_cflags=$(libgcrypt-config --cflags)
+        gcrypt_libs=$(libgcrypt-config --libs)
         # Debian has remove -lgpg-error from libgcrypt-config
         # as it "spreads unnecessary dependencies" which in
         # turn breaks static builds...
@@ -2334,9 +2334,9 @@  fi
 
 if test "$nettle" != "no"; then
     if $pkg_config --exists "nettle"; then
-        nettle_cflags=`$pkg_config --cflags nettle`
-        nettle_libs=`$pkg_config --libs nettle`
-        nettle_version=`$pkg_config --modversion nettle`
+        nettle_cflags=$($pkg_config --cflags nettle)
+        nettle_libs=$($pkg_config --libs nettle)
+        nettle_version=$($pkg_config --modversion nettle)
         libs_softmmu="$nettle_libs $libs_softmmu"
         libs_tools="$nettle_libs $libs_tools"
         QEMU_CFLAGS="$QEMU_CFLAGS $nettle_cflags"
@@ -2373,8 +2373,8 @@  tasn1=yes
 tasn1_cflags=""
 tasn1_libs=""
 if $pkg_config --exists "libtasn1"; then
-    tasn1_cflags=`$pkg_config --cflags libtasn1`
-    tasn1_libs=`$pkg_config --libs libtasn1`
+    tasn1_cflags=$($pkg_config --cflags libtasn1)
+    tasn1_libs=$($pkg_config --libs libtasn1)
 else
     tasn1=no
 fi
@@ -2404,9 +2404,9 @@  if test "$vte" != "no"; then
       vteminversion="0.24.0"
     fi
     if $pkg_config --exists "$vtepackage >= $vteminversion"; then
-        vte_cflags=`$pkg_config --cflags $vtepackage`
-        vte_libs=`$pkg_config --libs $vtepackage`
-        vteversion=`$pkg_config --modversion $vtepackage`
+        vte_cflags=$($pkg_config --cflags $vtepackage)
+        vte_libs=$($pkg_config --libs $vtepackage)
+        vteversion=$($pkg_config --modversion $vtepackage)
         libs_softmmu="$vte_libs $libs_softmmu"
         vte="yes"
     elif test "$vte" = "yes"; then
@@ -2447,16 +2447,16 @@  else
     error_exit "Unknown sdlabi $sdlabi, must be 1.2 or 2.0"
 fi
 
-if test "`basename $sdl_config`" != $sdlconfigname && ! has ${sdl_config}; then
+if test "$(basename $sdl_config)" != $sdlconfigname && ! has ${sdl_config}; then
   sdl_config=$sdlconfigname
 fi
 
 if $pkg_config $sdlname --exists; then
   sdlconfig="$pkg_config $sdlname"
-  sdlversion=`$sdlconfig --modversion 2>/dev/null`
+  sdlversion=$($sdlconfig --modversion 2>/dev/null)
 elif has ${sdl_config}; then
   sdlconfig="$sdl_config"
-  sdlversion=`$sdlconfig --version`
+  sdlversion=$($sdlconfig --version)
 else
   if test "$sdl" = "yes" ; then
     feature_not_found "sdl" "Install SDL devel"
@@ -2474,14 +2474,14 @@  if test "$sdl" != "no" ; then
 #undef main /* We don't want SDL to override our main() */
 int main( void ) { return SDL_Init (SDL_INIT_VIDEO); }
 EOF
-  sdl_cflags=`$sdlconfig --cflags 2> /dev/null`
+  sdl_cflags=$($sdlconfig --cflags 2>/dev/null)
   if test "$static" = "yes" ; then
-    sdl_libs=`$sdlconfig --static-libs 2>/dev/null`
+    sdl_libs=$($sdlconfig --static-libs 2>/dev/null)
   else
-    sdl_libs=`$sdlconfig --libs 2> /dev/null`
+    sdl_libs=$($sdlconfig --libs 2>/dev/null)
   fi
   if compile_prog "$sdl_cflags" "$sdl_libs" ; then
-    if test `echo $sdlversion | sed 's/[^0-9]//g'` -lt 121 ; then
+    if test $(echo $sdlversion | sed 's/[^0-9]//g') -lt 121 ; then
       sdl_too_old=yes
     else
       sdl=yes
@@ -2490,8 +2490,8 @@  EOF
     # static link with sdl ? (note: sdl.pc's --static --libs is broken)
     if test "$sdl" = "yes" -a "$static" = "yes" ; then
       if test $? = 0 && echo $sdl_libs | grep -- -laa > /dev/null; then
-         sdl_libs="$sdl_libs `aalib-config --static-libs 2>/dev/null`"
-         sdl_cflags="$sdl_cflags `aalib-config --cflags 2>/dev/null`"
+         sdl_libs="$sdl_libs $(aalib-config --static-libs 2>/dev/null)"
+         sdl_cflags="$sdl_cflags $(aalib-config --cflags 2>/dev/null)"
       fi
       if compile_prog "$sdl_cflags" "$sdl_libs" ; then
 	:
@@ -2608,8 +2608,8 @@  int main(void) {
 }
 EOF
   if $pkg_config libpng --exists; then
-    vnc_png_cflags=`$pkg_config libpng --cflags`
-    vnc_png_libs=`$pkg_config libpng --libs`
+    vnc_png_cflags=$($pkg_config libpng --cflags)
+    vnc_png_libs=$($pkg_config libpng --libs)
   else
     vnc_png_cflags=""
     vnc_png_libs="-lpng"
@@ -2803,7 +2803,7 @@  EOF
     fi
 }
 
-audio_drv_list=`echo "$audio_drv_list" | sed -e 's/,/ /g'`
+audio_drv_list=$(echo "$audio_drv_list" | sed -e 's/,/ /g')
 for drv in $audio_drv_list; do
     case $drv in
     alsa)
@@ -2915,8 +2915,8 @@  if test "$curl" != "no" ; then
 #include <curl/curl.h>
 int main(void) { curl_easy_init(); curl_multi_setopt(0, 0, 0); return 0; }
 EOF
-  curl_cflags=`$curlconfig --cflags 2>/dev/null`
-  curl_libs=`$curlconfig --libs 2>/dev/null`
+  curl_cflags=$($curlconfig --cflags 2>/dev/null)
+  curl_libs=$($curlconfig --libs 2>/dev/null)
   if compile_prog "$curl_cflags" "$curl_libs" ; then
     curl=yes
   else
@@ -2934,8 +2934,8 @@  if test "$bluez" != "no" ; then
 #include <bluetooth/bluetooth.h>
 int main(void) { return bt_error(0); }
 EOF
-  bluez_cflags=`$pkg_config --cflags bluez 2> /dev/null`
-  bluez_libs=`$pkg_config --libs bluez 2> /dev/null`
+  bluez_cflags=$($pkg_config --cflags bluez 2>/dev/null)
+  bluez_libs=$($pkg_config --libs bluez 2>/dev/null)
   if compile_prog "$bluez_cflags" "$bluez_libs" ; then
     bluez=yes
     libs_softmmu="$bluez_libs $libs_softmmu"
@@ -2958,8 +2958,8 @@  fi
 
 for i in $glib_modules; do
     if $pkg_config --atleast-version=$glib_req_ver $i; then
-        glib_cflags=`$pkg_config --cflags $i`
-        glib_libs=`$pkg_config --libs $i`
+        glib_cflags=$($pkg_config --cflags $i)
+        glib_libs=$($pkg_config --libs $i)
         CFLAGS="$glib_cflags $CFLAGS"
         LIBS="$glib_libs $LIBS"
         libs_qga="$glib_libs $libs_qga"
@@ -3048,8 +3048,8 @@  if test "$pixman" = "none"; then
   pixman_libs=
 elif test "$pixman" = "system"; then
   # pixman version has been checked above
-  pixman_cflags=`$pkg_config --cflags pixman-1`
-  pixman_libs=`$pkg_config --libs pixman-1`
+  pixman_cflags=$($pkg_config --cflags pixman-1)
+  pixman_libs=$($pkg_config --libs pixman-1)
 else
   if test ! -d ${source_path}/pixman/pixman; then
     error_exit "pixman >= 0.21.8 not present. Your options:" \
@@ -3165,8 +3165,8 @@  fi
 min_libssh2_version=1.2.8
 if test "$libssh2" != "no" ; then
   if $pkg_config --atleast-version=$min_libssh2_version libssh2; then
-    libssh2_cflags=`$pkg_config libssh2 --cflags`
-    libssh2_libs=`$pkg_config libssh2 --libs`
+    libssh2_cflags=$($pkg_config libssh2 --cflags)
+    libssh2_libs=$($pkg_config libssh2 --libs)
     libssh2=yes
   else
     if test "$libssh2" = "yes" ; then
@@ -3417,8 +3417,8 @@  fi
 if test "$glusterfs" != "no" ; then
   if $pkg_config --atleast-version=3 glusterfs-api; then
     glusterfs="yes"
-    glusterfs_cflags=`$pkg_config --cflags glusterfs-api`
-    glusterfs_libs=`$pkg_config --libs glusterfs-api`
+    glusterfs_cflags=$($pkg_config --cflags glusterfs-api)
+    glusterfs_libs=$($pkg_config --libs glusterfs-api)
     if $pkg_config --atleast-version=4 glusterfs-api; then
       glusterfs_xlator_opt="yes"
     fi
@@ -4225,12 +4225,12 @@  int main(void) { return 0; }
 EOF
   if compile_prog "" "" ; then
     if $pkg_config lttng-ust --exists; then
-      lttng_ust_libs=`$pkg_config --libs lttng-ust`
+      lttng_ust_libs=$($pkg_config --libs lttng-ust)
     else
       lttng_ust_libs="-llttng-ust"
     fi
     if $pkg_config liburcu-bp --exists; then
-      urcu_bp_libs=`$pkg_config --libs liburcu-bp`
+      urcu_bp_libs=$($pkg_config --libs liburcu-bp)
     else
       urcu_bp_libs="-lurcu-bp"
     fi
@@ -4670,10 +4670,10 @@  if test "$guest_agent_msi" = "yes"; then
   fi
 
   if test "$QEMU_GA_VERSION" = ""; then
-      QEMU_GA_VERSION=`cat $source_path/VERSION`
+      QEMU_GA_VERSION=$(cat $source_path/VERSION)
   fi
 
-  QEMU_GA_MSI_MINGW_DLL_PATH="-D Mingw_dlls=`$pkg_config --variable=prefix glib-2.0`/bin"
+  QEMU_GA_MSI_MINGW_DLL_PATH="-D Mingw_dlls=$($pkg_config --variable=prefix glib-2.0)/bin"
 
   case "$cpu" in
   x86_64)
@@ -4747,16 +4747,16 @@  QEMU_CFLAGS="$pixman_cflags $fdt_cflags $QEMU_CFLAGS"
 libs_softmmu="$pixman_libs $libs_softmmu"
 
 echo "Install prefix    $prefix"
-echo "BIOS directory    `eval echo $qemu_datadir`"
-echo "binary directory  `eval echo $bindir`"
-echo "library directory `eval echo $libdir`"
-echo "module directory  `eval echo $qemu_moddir`"
-echo "libexec directory `eval echo $libexecdir`"
-echo "include directory `eval echo $includedir`"
-echo "config directory  `eval echo $sysconfdir`"
+echo "BIOS directory    $(eval echo $qemu_datadir)"
+echo "binary directory  $(eval echo $bindir)"
+echo "library directory $(eval echo $libdir)"
+echo "module directory  $(eval echo $qemu_moddir)"
+echo "libexec directory $(eval echo $libexecdir)"
+echo "include directory $(eval echo $includedir)"
+echo "config directory  $(eval echo $sysconfdir)"
 if test "$mingw32" = "no" ; then
-echo "local state directory   `eval echo $local_statedir`"
-echo "Manual directory  `eval echo $mandir`"
+echo "local state directory   $(eval echo $local_statedir)"
+echo "Manual directory  $(eval echo $mandir)"
 echo "ELF interp prefix $interp_prefix"
 else
 echo "local state directory   queried at runtime"
@@ -4791,16 +4791,16 @@  if test "$darwin" = "yes" ; then
     echo "Cocoa support     $cocoa"
 fi
 echo "pixman            $pixman"
-echo "SDL support       $sdl `echo_version $sdl $sdlversion`"
-echo "GTK support       $gtk `echo_version $gtk $gtk_version`"
+echo "SDL support       $sdl $(echo_version $sdl $sdlversion)"
+echo "GTK support       $gtk $(echo_version $gtk $gtk_version)"
 echo "GTK GL support    $gtk_gl"
-echo "VTE support       $vte `echo_version $vte $vteversion`"
+echo "VTE support       $vte $(echo_version $vte $vteversion)"
 echo "GNUTLS support    $gnutls"
 echo "GNUTLS hash       $gnutls_hash"
 echo "GNUTLS rnd        $gnutls_rnd"
 echo "libgcrypt         $gcrypt"
 echo "libgcrypt kdf     $gcrypt_kdf"
-echo "nettle            $nettle `echo_version $nettle $nettle_version`"
+echo "nettle            $nettle $(echo_version $nettle $nettle_version)"
 echo "nettle kdf        $nettle_kdf"
 echo "libtasn1          $tasn1"
 echo "curses support    $curses"
@@ -4851,7 +4851,7 @@  echo "Trace backends    $trace_backends"
 if have_backend "simple"; then
 echo "Trace output file $trace_file-<pid>"
 fi
-echo "spice support     $spice `echo_version $spice $spice_protocol_version/$spice_server_version`"
+echo "spice support     $spice $(echo_version $spice $spice_protocol_version/$spice_server_version)"
 echo "rbd support       $rbd"
 echo "xfsctl support    $xfs"
 echo "smartcard support $smartcard"
@@ -4930,7 +4930,7 @@  if test "$bigendian" = "yes" ; then
 fi
 if test "$mingw32" = "yes" ; then
   echo "CONFIG_WIN32=y" >> $config_host_mak
-  rc_version=`cat $source_path/VERSION`
+  rc_version=$(cat $source_path/VERSION)
   version_major=${rc_version%%.*}
   rc_version=${rc_version#*.}
   version_minor=${rc_version%%.*}
@@ -5006,7 +5006,7 @@  if test "$cap_ng" = "yes" ; then
 fi
 echo "CONFIG_AUDIO_DRIVERS=$audio_drv_list" >> $config_host_mak
 for drv in $audio_drv_list; do
-    def=CONFIG_`echo $drv | LC_ALL=C tr '[a-z]' '[A-Z]'`
+    def=CONFIG_$(echo $drv | LC_ALL=C tr '[a-z]' '[A-Z]')
     echo "$def=y" >> $config_host_mak
 done
 if test "$audio_pt_int" = "yes" ; then
@@ -5038,7 +5038,7 @@  fi
 if test "$xfs" = "yes" ; then
   echo "CONFIG_XFS=y" >> $config_host_mak
 fi
-qemu_version=`head $source_path/VERSION`
+qemu_version=$(head $source_path/VERSION)
 echo "VERSION=$qemu_version" >>$config_host_mak
 echo "PKGVERSION=$pkgversion" >>$config_host_mak
 echo "SRC_PATH=$source_path" >> $config_host_mak
@@ -5049,7 +5049,7 @@  fi
 if test "$modules" = "yes"; then
   # $shacmd can generate a hash started with digit, which the compiler doesn't
   # like as an symbol. So prefix it with an underscore
-  echo "CONFIG_STAMP=_`(echo $qemu_version; echo $pkgversion; cat $0) | $shacmd - | cut -f1 -d\ `" >> $config_host_mak
+  echo "CONFIG_STAMP=_$( (echo $qemu_version; echo $pkgversion; cat $0) | $shacmd - | cut -f1 -d\ )" >> $config_host_mak
   echo "CONFIG_MODULES=y" >> $config_host_mak
 fi
 if test "$sdl" = "yes" ; then
@@ -5577,7 +5577,7 @@  fi
 for target in $target_list; do
 target_dir="$target"
 config_target_mak=$target_dir/config-target.mak
-target_name=`echo $target | cut -d '-' -f 1`
+target_name=$(echo $target | cut -d '-' -f 1)
 target_bigendian="no"
 
 case "$target_name" in
@@ -5617,7 +5617,7 @@  mkdir -p $target_dir
 echo "# Automatically generated by configure - do not modify" > $config_target_mak
 
 bflt="no"
-interp_prefix1=`echo "$interp_prefix" | sed "s/%M/$target_name/g"`
+interp_prefix1=$(echo "$interp_prefix" | sed "s/%M/$target_name/g")
 gdb_xml_files=""
 
 TARGET_ARCH="$target_name"
@@ -5743,7 +5743,7 @@  upper() {
     echo "$@"| LC_ALL=C tr '[a-z]' '[A-Z]'
 }
 
-target_arch_name="`upper $TARGET_ARCH`"
+target_arch_name="$(upper $TARGET_ARCH)"
 echo "TARGET_$target_arch_name=y" >> $config_target_mak
 echo "TARGET_NAME=$target_name" >> $config_target_mak
 echo "TARGET_BASE_ARCH=$TARGET_BASE_ARCH" >> $config_target_mak
@@ -5959,11 +5959,11 @@  for bios_file in \
     $source_path/pc-bios/u-boot.* \
     $source_path/pc-bios/palcode-*
 do
-    FILES="$FILES pc-bios/`basename $bios_file`"
+    FILES="$FILES pc-bios/$(basename $bios_file)"
 done
-for test_file in `find $source_path/tests/acpi-test-data -type f`
+for test_file in $(find $source_path/tests/acpi-test-data -type f)
 do
-    FILES="$FILES tests/acpi-test-data`echo $test_file | sed -e 's/.*acpi-test-data//'`"
+    FILES="$FILES tests/acpi-test-data$(echo $test_file | sed -e 's/.*acpi-test-data//')"
 done
 mkdir -p $DIRS
 for f in $FILES ; do