Use a helper function to tidy the assembly of gcc_flags.
Separate flags that disable warnings from those that enable,
and sort the disable warnings to the end.

Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 configure | 40 ++++++++++++++++++++++++++++++----------
 1 file changed, 30 insertions(+), 10 deletions(-)

diff --git a/configure b/configure
index 597e909b53..464202e375 100755
--- a/configure
+++ b/configure
@@ -97,6 +97,11 @@ do_cxx() {
     do_compiler "$cxx" "$@"
 }
 
+# Append $2 to the variable named $1, with space separation
+add_to() {
+    eval $1=\${$1:+\"\$$1 \"}\$2
+}
+
 update_cxxflags() {
     # Set QEMU_CXXFLAGS from QEMU_CFLAGS by filtering out those
     # options which some versions of GCC's C++ compiler complain about
@@ -2007,16 +2012,31 @@ if ! compile_prog "" "" ; then
     error_exit "You need at least GCC v4.8 or Clang v3.4 (or XCode Clang v5.1)"
 fi
 
-gcc_flags="-Wold-style-declaration -Wold-style-definition -Wtype-limits"
-gcc_flags="-Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers $gcc_flags"
-gcc_flags="-Wno-missing-include-dirs -Wempty-body -Wnested-externs $gcc_flags"
-gcc_flags="-Wendif-labels -Wno-shift-negative-value $gcc_flags"
-gcc_flags="-Wno-initializer-overrides -Wexpansion-to-defined $gcc_flags"
-gcc_flags="-Wno-string-plus-int -Wno-typedef-redefinition $gcc_flags"
-# Note that we do not add -Werror to gcc_flags here, because that would
-# enable it for all configure tests. If a configure test failed due
-# to -Werror this would just silently disable some features,
-# so it's too error prone.
+# Accumulate -Wfoo and -Wno-bar separately.
+# We will list all of the enable flags first, and the disable flags second.
+# Note that we do not add -Werror, because that would enable it for all
+# configure tests. If a configure test failed due to -Werror this would
+# just silently disable some features, so it's too error prone.
+
+add_to warn_flags -Wold-style-declaration
+add_to warn_flags -Wold-style-definition
+add_to warn_flags -Wtype-limits
+add_to warn_flags -Wformat-security
+add_to warn_flags -Wformat-y2k
+add_to warn_flags -Winit-self
+add_to warn_flags -Wignored-qualifiers
+add_to warn_flags -Wempty-body
+add_to warn_flags -Wnested-externs
+add_to warn_flags -Wendif-labels
+add_to warn_flags -Wno-initializer-overrides
+add_to warn_flags -Wexpansion-to-defined
+
+add_to nowarn_flags -Wno-missing-include-dirs
+add_to nowarn_flags -Wno-shift-negative-value
+add_to nowarn_flags -Wno-string-plus-int
+add_to nowarn_flags -Wno-typedef-redefinition
+
+gcc_flags="$warn_flags $nowarn_flags"
 
 cc_has_warning_flag() {
     write_c_skeleton;
-- 
2.25.1

On 6/10/20 3:39 PM, Richard Henderson wrote:
> Use a helper function to tidy the assembly of gcc_flags.
> Separate flags that disable warnings from those that enable,
> and sort the disable warnings to the end.
> 
> Suggested-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   configure | 40 ++++++++++++++++++++++++++++++----------
>   1 file changed, 30 insertions(+), 10 deletions(-)
> 

> +# Accumulate -Wfoo and -Wno-bar separately.
> +# We will list all of the enable flags first, and the disable flags second.
> +# Note that we do not add -Werror, because that would enable it for all
> +# configure tests. If a configure test failed due to -Werror this would
> +# just silently disable some features, so it's too error prone.
> +
> +add_to warn_flags -Wold-style-declaration

Hmm - should we add:
warn_flags= nowarn_flags=
prior to this line, to ensure that something inherited from the 
environment doesn't mess us up.

> +add_to warn_flags -Wold-style-definition
> +add_to warn_flags -Wtype-limits
> +add_to warn_flags -Wformat-security
> +add_to warn_flags -Wformat-y2k
> +add_to warn_flags -Winit-self
> +add_to warn_flags -Wignored-qualifiers
> +add_to warn_flags -Wempty-body
> +add_to warn_flags -Wnested-externs
> +add_to warn_flags -Wendif-labels
> +add_to warn_flags -Wno-initializer-overrides

wrong list

> +add_to warn_flags -Wexpansion-to-defined
> +
> +add_to nowarn_flags -Wno-missing-include-dirs
> +add_to nowarn_flags -Wno-shift-negative-value
> +add_to nowarn_flags -Wno-string-plus-int
> +add_to nowarn_flags -Wno-typedef-redefinition
> +
> +gcc_flags="$warn_flags $nowarn_flags"

Otherwise looks sane.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

On 6/11/20 7:25 AM, Eric Blake wrote:
>> +add_to warn_flags -Wold-style-declaration
> 
> Hmm - should we add:
> warn_flags= nowarn_flags=
> prior to this line, to ensure that something inherited from the environment
> doesn't mess us up.
> 
>> +add_to warn_flags -Wold-style-definition
>> +add_to warn_flags -Wtype-limits
>> +add_to warn_flags -Wformat-security
>> +add_to warn_flags -Wformat-y2k
>> +add_to warn_flags -Winit-self
>> +add_to warn_flags -Wignored-qualifiers
>> +add_to warn_flags -Wempty-body
>> +add_to warn_flags -Wnested-externs
>> +add_to warn_flags -Wendif-labels
>> +add_to warn_flags -Wno-initializer-overrides
> 
> wrong list

Thanks, fixed both.


r~