Avoid potential zero size array declaration; fix #4382

include/mruby/array.h

@@ -33,7 +33,6 @@ struct RArray {
       } aux;
       mrb_value *ptr;
     } heap;
-    mrb_value embed[MRB_ARY_EMBED_LEN_MAX];
   } as;
 };
 
@@ -46,7 +45,7 @@ struct RArray {
 #define ARY_UNSET_EMBED_FLAG(a) ((a)->flags &= ~(MRB_ARY_EMBED_MASK))
 #define ARY_EMBED_LEN(a) ((mrb_int)(((a)->flags & MRB_ARY_EMBED_MASK) - 1))
 #define ARY_SET_EMBED_LEN(a,len) ((a)->flags = ((a)->flags&~MRB_ARY_EMBED_MASK) | ((uint32_t)(len) + 1))
-#define ARY_EMBED_PTR(a) (&((a)->as.embed[0]))
+#define ARY_EMBED_PTR(a) ((mrb_value*)&(a)->as)
 
 #define ARY_LEN(a) (ARY_EMBED_P(a)?ARY_EMBED_LEN(a):(a)->as.heap.len)
 #define ARY_PTR(a) (ARY_EMBED_P(a)?ARY_EMBED_PTR(a):(a)->as.heap.ptr)

tasks/toolchains/clang.rake

@@ -3,7 +3,9 @@ MRuby::Toolchain.new(:clang) do |conf, _params|
 
   [conf.cc, conf.objc, conf.asm].each do |cc|
     cc.command = ENV['CC'] || 'clang'
+    cc.flags << '-Wzero-length-array' unless ENV['CFLAGS']
   end
   conf.cxx.command = ENV['CXX'] || 'clang++'
+  conf.cxx.flags << '-Wzero-length-array' unless ENV['CXXFLAGS'] || ENV['CFLAGS']
   conf.linker.command = ENV['LD'] || ENV['CXX'] || ENV['CC'] || 'clang'
 end