Allow the last member of a struct to be an unsized/zero-length array.

This enables the C truck of allocating a dynamic amount of storage for
the struct in order to extend out the array to the desired length.

decl.cpp

@@ -739,15 +739,7 @@ GetStructTypesNamesPositions(const std::vector<StructDeclaration *> &sd,
             if (Type::Equal(sym->type, AtomicType::Void))
                 Error(d->pos, "\"void\" type illegal for struct member.");
 
-            const ArrayType *arrayType = 
-                dynamic_cast<const ArrayType *>(sym->type);
-            if (arrayType != NULL && arrayType->GetElementCount() == 0) {
-                Error(d->pos, "Unsized arrays aren't allowed in struct "
-                      "definitions.");
-                elementTypes->push_back(NULL);
-            }
-            else
-                elementTypes->push_back(sym->type);
+            elementTypes->push_back(sym->type);
 
             if (seenNames.find(sym->name) != seenNames.end())
                 Error(d->pos, "Struct member \"%s\" has same name as a "
@@ -759,4 +751,13 @@ GetStructTypesNamesPositions(const std::vector<StructDeclaration *> &sd,
             elementPositions->push_back(sym->pos);
         }
     }
+
+    for (int i = 0; i < (int)elementTypes->size() - 1; ++i) {
+        const ArrayType *arrayType = 
+            dynamic_cast<const ArrayType *>((*elementTypes)[i]);
+
+        if (arrayType != NULL && arrayType->GetElementCount() == 0)
+            Error((*elementPositions)[i], "Unsized arrays aren't allowed except "
+                  "for the last member in a struct definition.");
+    }
 }

tests/struct-zero-len-array-member.ispc

@@ -0,0 +1,24 @@
+
+struct Foo {
+    float x;
+    float a[0];
+};
+
+export uniform int width() { return programCount; }
+
+
+export void f_f(uniform float RET[], uniform float aFOO[]) {
+    uniform int nFloats = 3+programCount;
+    varying Foo * uniform ptr = (varying Foo * uniform)(uniform new varying int32[nFloats]);
+    memset(ptr, 0, nFloats*sizeof(int32));
+    
+    for (uniform int i = 0; i < nFloats-1; ++i)
+        ptr->a[i] = i;
+    ptr->x = aFOO[programIndex]; 
+
+    RET[programIndex] = ptr->a[1+programIndex]; 
+}
+
+export void result(uniform float RET[]) {
+    RET[programIndex] = 1 + programIndex;
+}

tests_errors/struct-unsized-array.ispc

@@ -1,4 +1,4 @@
-// Unsized arrays aren't allowed in struct definitions
+// Unsized arrays aren't allowed except for the last member in a struct definition.
 
 struct Foo {
     float a[];