Revert "Stop using -std=gnu*"

This reverts commit c85c6c91.

Reason for revert: Broke AFL ASan builder
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Afl%20Upload%20Linux%20ASan

Original change's description:
> Stop using -std=gnu*
> 
> BUG=427584
> R=​thakis
> TBR=sbc
> 
> Change-Id: I4a6f67aa6ddaf8ab78719a3c925fcd732b8c28bf
> Reviewed-on: https://chromium-review.googlesource.com/1149337
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#581478}

TBR=thakis@chromium.org,thomasanderson@chromium.org

Change-Id: Ie673c185580662fad3d641000edfc4ee203acf9a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 427584
Reviewed-on: https://chromium-review.googlesource.com/1166663Reviewed-by: Abhishek Arya <inferno@chromium.org>
Commit-Queue: Abhishek Arya <inferno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581481}

build/config/compiler/BUILD.gn

@@ -547,22 +547,16 @@ config("compiler") {
       cxx11_override = use_cxx11
     }
 
-    # Since we build with -std=c* and not -std=gnu*, _GNU_SOURCE will not be
-    # defined by the compiler.  However, lots of code relies on the non-standard
-    # features that _GNU_SOURCE enables, so define it manually.
-    defines += [ "_GNU_SOURCE" ]
-
-    cflags_c += [ "-std=c11" ]
+    # gnu11/gnu++11 instead of c11/c++11 is needed because some code uses typeof()
+    # (a GNU extension).
+    # TODO(thakis): Eventually switch this to c++11 instead,
+    # http://crbug.com/427584
+    cflags_c += [ "-std=gnu11" ]
     if (cxx11_override) {
       # Override Chromium's default for projects that wish to stay on C++11.
-      cflags_cc += [ "-std=c++11" ]
+      cflags_cc += [ "-std=gnu++11" ]
     } else {
-      cflags_cc += [ "-std=c++14" ]
-    }
-    if (is_nacl) {
-      # Undefine __STRICT_ANSI__ to get non-standard features which would
-      # otherwise not be enabled by NaCl's sysroots.
-      cflags += [ "-U__STRICT_ANSI__" ]
+      cflags_cc += [ "-std=gnu++14" ]
     }
   } else if (!is_win && !is_nacl) {
     if (target_os == "android") {

native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.cc

@@ -82,7 +82,7 @@ EXTERN_C_BEGIN
 #define WRAP(name) __nacl_irt_##name##_wrap
 
 // Declare REAL function pointer.
-#define DECLARE_REAL_PTR(name) __typeof__(__nacl_irt_##name) REAL(name);
+#define DECLARE_REAL_PTR(name) typeof(__nacl_irt_##name) REAL(name);
 
 // Assign the REAL function pointer.
 #define ASSIGN_REAL_PTR(name)        \
@@ -90,12 +90,10 @@ EXTERN_C_BEGIN
   REAL(name) = __nacl_irt_##name;
 
 // Switch IRT's pointer to the REAL pointer
-#define USE_REAL(name) \
-  __nacl_irt_##name = (__typeof__(__nacl_irt_##name))REAL(name)
+#define USE_REAL(name) __nacl_irt_##name = (typeof(__nacl_irt_##name))REAL(name)
 
 // Switch IRT's pointer to the WRAP function
-#define USE_WRAP(name) \
-  __nacl_irt_##name = (__typeof__(__nacl_irt_##name))WRAP(name)
+#define USE_WRAP(name) __nacl_irt_##name = (typeof(__nacl_irt_##name))WRAP(name)
 
 #define EXPAND_SYMBOL_LIST_OPERATION(OP) \
   OP(chdir);                             \

native_client_sdk/src/libraries/nacl_io/kernel_wrap_newlib.cc

@@ -32,18 +32,18 @@ EXTERN_C_BEGIN
 
 // Declare REAL function pointer.
 #define DECLARE_REAL_PTR(group, name) \
-  __typeof__(__libnacl_irt_##group.name) REAL(name);
+  typeof(__libnacl_irt_##group.name) REAL(name);
 
 // Assign the REAL function pointer.
 #define ASSIGN_REAL_PTR(group, name) REAL(name) = __libnacl_irt_##group.name;
 
 // Switch IRT's pointer to the REAL pointer
 #define USE_REAL(group, name) \
-  __libnacl_irt_##group.name = (__typeof__(REAL(name)))REAL(name);
+  __libnacl_irt_##group.name = (typeof(REAL(name)))REAL(name);
 
 // Switch the IRT's pointer to the WRAP function
 #define USE_WRAP(group, name) \
-  __libnacl_irt_##group.name = (__typeof__(REAL(name)))WRAP(name);
+  __libnacl_irt_##group.name = (typeof(REAL(name)))WRAP(name);
 
 extern void __libnacl_irt_dev_filename_init(void);
 extern void __libnacl_irt_dev_fdio_init(void);

third_party/libdrm/BUILD.gn

@@ -15,10 +15,8 @@ declare_args() {
 
 if (!use_system_libdrm) {
   config("libdrm_config") {
-    # TODO(thomasanderson): Remove this hack once
-    # https://patchwork.kernel.org/patch/10545295/ lands.
-    defines = [ "typeof(x)=__typeof__(x)" ]
-
+    # Define _GNU_SOURCE for vasprintf use in xf86drm.c
+    defines = [ "_GNU_SOURCE" ]
     include_dirs = [
       "src",
       "src/include",

third_party/wayland/BUILD.gn

@@ -16,10 +16,6 @@ if (!use_system_libwayland) {
       "include/protocol",
       "src/src",
     ]
-
-    # TODO(thomasanderson): Remove this once
-    # https://patchwork.freedesktop.org/patch/242086/ lands.
-    cflags = [ "-Wno-macro-redefined" ]
   }
 
   static_library("wayland_util") {