std::string with custom allocator in protobuf message

Question

I need a string field in a Protobuf message to use a custom allocator for its internal char* buffer, instead of the default global allocator.

I am aware that google::protobuf::Arena will allocate the std::string object itself in the arena, but this does not affect the allocator used for that string's internal data buffer.

Ideally, I'd like the field to be a std::basic_string<..., MyCustomAllocator>. The [ctype] option seems limited to CORD and STRING_PIECE and doesn't appear to support arbitrary types.

Is there any way to control the allocator for a string field?

I am also considering using std::string_view. The idea is to define string_view field in my .proto and then manage the memory for the string buffer myself, outside of Protobuf. Do you see any pitfalls with this approach?

There is no built-in way to control the allocator for a string field's internal buffer in protobuf. If allocator control is critical, you may need to manage the memory outside of protobuf and use bytes or a custom wrapper. — Ranadip Dutta
– Ranadip Dutta, Commented Jun 9 at 8:22

Njrslv-yndx-cloud · Accepted Answer · 2025-07-09 11:10:24Z

0

The solution for me was to upgrade protobuf and use absl::string_view instead of std::string in my proto messages.

// message.proto
edition = "2023";

import "google/protobuf/cpp_features.proto";
option features.(pb.cpp).string_type=VIEW;
// Now each string field will be string_view in generated code.

answered Jul 9 at 11:10

Njrslv-yndx-cloud

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