libstdc++ (GCC) Source-Level Deep Analysis

Source path: references/impl/gcc/libstdc++-v3/include/

GCC's C++ standard library implementation, the de facto standard in the Linux ecosystem. Core design philosophy: ABI stability takes priority over aggressive optimization.

Table of Contents

Chapter	Content
string ABI Migration	COW → SSO migration, dual ABI coexistence, __cxx11 namespace
vector and _Hashtable	vector growth strategy, unordered_map node-based _Hashtable
shared_ptr / RB-tree / function	Control block, _Rb_tree sentinel node, function pointer SBO

Three-Implementation Comparison

Component	libstdc++ (GCC)	libc++ (LLVM)	MSVC STL
sizeof(string)	32	24	32
string SSO	15	22	15
string COW	yes (ABI v1)	no	no
vector relocate	move+destroy	memcpy	move+destroy
function polymorphism	function pointer	vtable	function pointer
unordered_map	node-based _Hashtable	chaining	chaining
ABI stability	strongest (abi_tag)	versioned	strong

Choose libstdc++ for: Linux servers, strongest ABI compatibility, conservative and stable implementation strategy, HPC.