forked from OSchip/llvm-project
[ADT] Add llvm::StringLiteral.
StringLiteral is a wrapper around a string literal useful for replacing global tables of char arrays with global tables of StringRefs that can initialized in a constexpr context, avoiding the invocation of a global constructor. Differential Revision: https://reviews.llvm.org/D27686 llvm-svn: 289551
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@ -84,11 +84,8 @@ namespace llvm {
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/// Construct a string ref from a pointer and length.
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LLVM_ATTRIBUTE_ALWAYS_INLINE
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/*implicit*/ StringRef(const char *data, size_t length)
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: Data(data), Length(length) {
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assert((data || length == 0) &&
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"StringRef cannot be built from a NULL argument with non-null length");
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}
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/*implicit*/ constexpr StringRef(const char *data, size_t length)
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: Data(data), Length(length) {}
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/// Construct a string ref from an std::string.
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LLVM_ATTRIBUTE_ALWAYS_INLINE
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@ -839,6 +836,26 @@ namespace llvm {
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/// @}
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};
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/// A wrapper around a string literal that serves as a proxy for constructing
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/// global tables of StringRefs with the length computed at compile time.
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/// Using this class with a non-literal char array is considered undefined
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/// behavior. To prevent this, it is recommended that StringLiteral *only*
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/// be used in a constexpr context, as such:
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///
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/// constexpr StringLiteral S("test");
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///
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/// Note: There is a subtle behavioral difference in the constructor of
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/// StringRef and StringLiteral, as illustrated below:
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///
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/// constexpr StringLiteral S("a\0b"); // S.size() == 3
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/// StringRef S("a\0b"); // S.size() == 1
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///
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class StringLiteral : public StringRef {
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public:
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template <size_t N>
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constexpr StringLiteral(const char (&Str)[N]) : StringRef(Str, N - 1) {}
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};
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/// @name StringRef Comparison Operators
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/// @{
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@ -1002,4 +1002,10 @@ TEST(StringRefTest, DropWhileUntil) {
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EXPECT_EQ("", Taken);
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}
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TEST(StringRefTest, StringLiteral) {
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constexpr StringLiteral Strings[] = {"Foo", "Bar"};
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EXPECT_EQ(StringRef("Foo"), Strings[0]);
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EXPECT_EQ(StringRef("Bar"), Strings[1]);
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}
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} // end anonymous namespace
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