Disable/avoid some warnings.

Implement DAWN_DECLARE_UNUSED macro to avoid -Wunneeded-internal-declaration
warning.

Change-Id: I4d087d2b09b74e35ba7ea69533df2c5adef4ef82
Reviewed-on: https://dawn-review.googlesource.com/c/2943
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Stephen White <senorblanco@chromium.org>

generator/templates/dawn_wire/WireCmd.cpp

@@ -110,7 +110,7 @@
     };
 
     //* Returns the required transfer size for `record` in addition to the transfer structure.
-    size_t {{name}}GetExtraRequiredSize(const {{name}}& record) {
+    DAWN_DECLARE_UNUSED size_t {{name}}GetExtraRequiredSize(const {{name}}& record) {
         DAWN_UNUSED(record);
 
         size_t result = 0;

src/common/Compiler.h

@@ -24,6 +24,9 @@
 //      (resp. false) to help it generate code that leads to better branch prediction.
 //  - DAWN_UNUSED(EXPR): Prevents unused variable/expression warnings on EXPR.
 //  - DAWN_UNUSED_FUNC(FUNC): Prevents unused function warnings on FUNC.
+//  - DAWN_DECLARE_UNUSED:    Prevents unused function warnings a subsequent declaration.
+//  Both DAWN_UNUSED_FUNC and DAWN_DECLARE_UNUSED may be necessary, e.g. to suppress clang's
+//  unneeded-internal-declaration warning.
 
 // Clang and GCC, check for __clang__ too to catch clang-cl masquarading as MSVC
 #if defined(__GNUC__) || defined(__clang__)
@@ -57,6 +60,8 @@
 #        define DAWN_NO_DISCARD [[nodiscard]]
 #    endif
 
+#    define DAWN_DECLARE_UNUSED __attribute__((unused))
+
 // MSVC
 #elif defined(_MSC_VER)
 #    define DAWN_COMPILER_MSVC
@@ -71,6 +76,8 @@ extern void __cdecl __debugbreak(void);
 #        define DAWN_NO_DISCARD [[nodiscard]]
 #    endif
 
+#    define DAWN_DECLARE_UNUSED
+
 #else
 #    error "Unsupported compiler"
 #endif

third_party/BUILD.gn

@@ -58,6 +58,9 @@ static_library("spirv_cross") {
       "-Wno-return-type",
       "-Wno-sign-compare",
     ]
+  } else {
+    # Disable "not all control paths return a value" warning.
+    cflags_cc = [ "/wd4715" ]
   }
 
   sources = [
@@ -211,7 +214,10 @@ static_library("glfw") {
     # nonstandard extension, function/data pointer conversion in expression
     cflags_c = [ "/wd4152" ]
   } else {
-    cflags_c = [ "-Wno-sign-compare" ]
+    cflags_c = [
+      "-Wno-sign-compare",
+      "-Wno-missing-field-initializers",
+    ]
   }
 
   sources = [