Fix uninitialized member (#8094)

std::array is an aggregate type with a C array as a member so its
default initialization is garbage. Change it to value initialization to
ensure that it has a defined value which removes the need for disabling
the warnings and fixes the Alpine CI build.

Author: stevenfontanella

src/support/small_vector.h

@@ -30,26 +30,10 @@
 
 namespace wasm {
 
-// We don't understand this warning, only here and only on aarch64 and riscv64,
-// we suspect it's spurious so disabling for now.
-//
-// For context: https://github.com/WebAssembly/binaryen/issues/6311
-
-#if defined(__aarch64__)
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
-#endif
-
-// https://github.com/WebAssembly/binaryen/issues/6410
-#if defined(__riscv) && __riscv_xlen == 64
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wuninitialized"
-#endif
-
 template<typename T, size_t N> class SmallVector {
   // fixed-space storage
   size_t usedFixed = 0;
-  std::array<T, N> fixed;
+  std::array<T, N> fixed{};
 
   // flexible additional storage
   std::vector<T> flexible;
@@ -246,14 +230,6 @@ struct ZeroInitSmallVector : public SmallVector<T, N> {
   }
 };
 
-#if defined(__aarch64__)
-#pragma GCC diagnostic pop
-#endif
-
-#if defined(__riscv) && __riscv_xlen == 64
-#pragma GCC diagnostic pop
-#endif
-
 } // namespace wasm
 
 #endif // wasm_support_small_vector_h