Delete -Wdeclaration-after-statement

Older versions of MSVC do not allow declarations after statements in C
files. We don't need to support those versions of MSVC now.

Use -std=gnu99 instead of -std=gnu89.

Change-Id: I76ba962f5a2bca30d6a5b2b05c5786507398ad32

2 files changed, 7 insertions, 4 deletions

diff --git a/CHANGELOG b/CHANGELOG
index f932f6bf4..5a8605a73 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,8 @@
+20yy-mm-dd v1.14.0 "V Duck"
+  This release drops support for old C compilers, such as Visual Studio 2012
+  and older, that disallow mixing variable declarations and statements (a C99
+  feature).
+
 2023-09-29 v1.13.1 "Ugly Duckling"
   This release contains two security related fixes. One each for VP8 and VP9.
 
diff --git a/configure b/configure
index 434c43792..6b910160a 100755
--- a/configure
+++ b/configure
@@ -643,7 +643,6 @@ process_toolchain() {
     if enabled gcc; then
         enabled werror && check_add_cflags -Werror
         check_add_cflags -Wall
-        check_add_cflags -Wdeclaration-after-statement
         check_add_cflags -Wdisabled-optimization
         check_add_cflags -Wextra-semi
         check_add_cflags -Wextra-semi-stmt
@@ -670,9 +669,8 @@ process_toolchain() {
         if enabled mips || [ -z "${INLINE}" ]; then
           enabled extra_warnings || check_add_cflags -Wno-unused-function
         fi
-        # Enforce c89 for c files. Don't be too strict about it though. Allow
-        # gnu extensions like "//" for comments.
-        check_cflags -std=gnu89 && add_cflags_only -std=gnu89
+        # Enforce C99 for C files. Allow GNU extensions.
+        check_cflags -std=gnu99 && add_cflags_only -std=gnu99
         # Avoid this warning for third_party C++ sources. Some reorganization
         # would be needed to apply this only to test/*.cc.
         check_cflags -Wshorten-64-to-32 && add_cflags_only -Wshorten-64-to-32