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forbid enum values that are out of range (#4977)

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* forbid enum values that are out of range

Enum values that are out of range can lead to generated C++ code that does
not compile.  Also forbid boolean enums.

* update enum and union documentation slightly
This commit is contained in:
Frank Benkstein
2018-10-18 19:39:08 +02:00
committed by Wouter van Oortmerssen
parent 802639e40d
commit 5c0f914f38
3 changed files with 78 additions and 12 deletions
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41
src/idl_parser.cpp
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@@ -1594,7 +1594,8 @@ CheckedError Parser::ParseEnum(bool is_union, EnumDef **dest) {
}
// Specify the integer type underlying this enum.
ECHECK(ParseType(enum_def->underlying_type));
if (!IsInteger(enum_def->underlying_type.base_type))
if (!IsInteger(enum_def->underlying_type.base_type) ||
IsBool(enum_def->underlying_type.base_type))
return Error("underlying enum type must be integral");
// Make this type refer back to the enum it was derived from.
enum_def->underlying_type.enum_def = enum_def;
@@ -1620,10 +1621,8 @@ CheckedError Parser::ParseEnum(bool is_union, EnumDef **dest) {
}
}
auto prevsize = enum_def->vals.vec.size();
auto value = !enum_def->vals.vec.empty()
? enum_def->vals.vec.back()->value + 1
: 0;
auto &ev = *new EnumVal(value_name, value);
auto prevvalue = prevsize > 0 ? enum_def->vals.vec.back()->value : 0;
auto &ev = *new EnumVal(value_name, 0);
if (enum_def->vals.Add(value_name, &ev))
return Error("enum value already exists: " + value_name);
ev.doc_comment = value_comment;
@@ -1646,11 +1645,37 @@ CheckedError Parser::ParseEnum(bool is_union, EnumDef **dest) {
if (!opts.proto_mode && prevsize &&
enum_def->vals.vec[prevsize - 1]->value >= ev.value)
return Error("enum values must be specified in ascending order");
} else if (prevsize == 0) {
// already set to zero
} else if (prevvalue != flatbuffers::numeric_limits<int64_t>::max()) {
ev.value = prevvalue + 1;
} else {
return Error("enum value overflows");
}
if (is_union) {
if (ev.value < 0 || ev.value >= 256)
return Error("union enum value must fit in a ubyte");
// Check that value fits into the underlying type.
switch (enum_def->underlying_type.base_type) {
// clang-format off
#define FLATBUFFERS_TD(ENUM, IDLTYPE, CTYPE, JTYPE, GTYPE, NTYPE, \
PTYPE, RTYPE) \
case BASE_TYPE_##ENUM: { \
int64_t min_value = static_cast<int64_t>( \
flatbuffers::numeric_limits<CTYPE>::lowest()); \
int64_t max_value = static_cast<int64_t>( \
flatbuffers::numeric_limits<CTYPE>::max()); \
if (ev.value < min_value || ev.value > max_value) { \
return Error( \
"enum value does not fit [" + NumToString(min_value) + \
"; " + NumToString(max_value) + "]"); \
} \
break; \
}
FLATBUFFERS_GEN_TYPES_SCALAR(FLATBUFFERS_TD);
#undef FLATBUFFERS_TD
default: break;
// clang-format on
}
if (opts.proto_mode && Is('[')) {
NEXT();
// ignore attributes on enums.