What Breaking Changes Should I Be Aware of When Migrating to C 11?

What Breaking Changes Are Introduced in C 11?

One of the significant changes introduced in C 11 is the explicit operator bool() in the standard library, replacing instances of operator void*(). While this change should address invalid code, there are other potential breaking changes to consider.

Core Language Incompatibilities

• Modified String Literals Interpretation: Predefined macros like "u8" may modify string literals.
• User-Defined String Literals: "_x" in string literals now creates user-defined string literals, instead of expanding macros.
• New Keywords: Introduced keywords like "constexpr" and "thread_local" can break existing identifier names.
• Integer Literal Modifications: Integer literals exceeding the range of "long" may now become "long long."
• Integer Division Modifications: C 03 integer division rounding behavior may differ from C 11's rounding toward 0.
• "auto" as Storage Specifier: C 03 code using "auto" as a storage specifier may become invalid.
• Narrowing Conversions: C 03 narrowing conversions (e.g., double to int) may now be invalid.
• Implicit Special Member Function Deletions: Ill-formed implicitly-defined member functions are automatically deleted.
• Destructor Exception Specifications: User-declared destructors now have implicit noexcept(true) specifications.
• "export" Declaration Elimination: C 03 declarations using "export" are now invalid.
• Template Closing Modification: ">>" in templates may now close two templates instead of being considered only as a shift operator.
• Dependent Calls of Internal Linkage Functions: Dependent calls of internal linkage functions are now allowed.

Library Modifications

• Namespaced Identifiers: Identifiers added to the standard library may break existing code.
• Header Includes: Headers previously located in certain standard headers (e.g., , ) may have moved elsewhere.
• "posix" Namespace: The "posix" namespace is now reserved for future standardization.
• Macro Definitions: Defining "override," "final," "carries_dependency," or "noreturn" as macros may now be invalid.

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