CODEWITHSUNDEEP
c++stringstdstring
truf
truf

Reputation: 3111

Disable std:string's SSO

I wonder if there is a way to programmatically disable string SSO to make it not use local buffer for short strings?

Upvotes: 5

Views: 2404

Answers (2)

Slion
Slion

Reputation: 3078

With GCC at compile time you can use the older Copy-On-Write std::string implementation over the newer Small String Optimisation (SSO) by adding the following to your CMake file:

add_compile_definitions(_GLIBCXX_USE_CXX11_ABI=0)

On a 32 bits architecture such as the Raspberry Pi Pico std::string weights 24 bytes with SSO and only 4 bytes with COW.

Upvotes: 1

Baum mit Augen
Baum mit Augen

Reputation: 50101

As SSO is an optional optimization, there won't be a standard way to turn it off.

In practice, you can just reserve a string that won't fit into the SSO buffer to force the buffer being allocated dynamically:

std::string str;
str.reserve(sizeof(str) + 1);

That seems to work for gcc at least and should even work portably as the internal buffer needs to fit inside the string. (Live)

Upvotes: 16

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