gen-c

This repo contains the templates used by the webrpc-gen CLI to code-generate webrpc C client code.

This generator, from a webrpc schema/design file, will code-generate:

1. Header output Public C enums, structs, support types, init / free helpers, client declarations, and lower-level request / response helpers.

2. Implementation output C JSON encode/decode helpers, generated method request / response handling, and an optional libcurl-based client runtime.

The generated client is intended to speak to any webrpc server language (Go, nodejs, etc.) as long as the schema features used are supported by this target.

Dependencies

Generated header output only depends on the C standard library headers included by the generated file.

Generated impl output currently depends on:

• cJSON
• libcurl

The generated code targets C99.

Typical compile / link flags look like:

cc -std=c99 \
  $(pkg-config --cflags libcurl libcjson) \
  -c example.gen.c

cc -std=c99 \
  app.c example.gen.c \
  $(pkg-config --cflags --libs libcurl libcjson) \
  -o app

Dependency names can vary slightly by platform or package manager. The important part is that the generated implementation can include <cjson/cJSON.h> and link against libcurl and cJSON.

Because the generated implementation uses cJSON, exact large 64-bit integer handling follows cJSON's numeric behavior. If your API needs exact integer round-tripping beyond normal JSON number precision expectations, prefer bigint in the schema instead of int64 / uint64.

Features

The current generator supports:

• client code generation
• separate header and impl emission
• generated DTO structs and enums
• generated init / free helpers for schema and method wrapper types
• bigint values encoded as JSON strings
• timestamp values encoded as JSON strings
• any, null, nested lists, nested maps, and nested structs
• map keys of type string and enum
• succinct method wire format
• generated lower-level helpers to:
  • prepare request bytes without sending them
  • send a prepared request with the generated transport
  • parse a raw HTTP response into generated response types
• generated libcurl client configuration for bearer auth, custom headers, and timeouts

Limitations

The current generator does not support:

• server generation
• streaming methods
• map keys other than string or enum
• a shared external transport abstraction; the generated runtime is currently self-contained

Implementation generation also assumes a companion generated header include via -header=<file>.

Usage

Generate the header:

webrpc-gen \
  -schema=example.ridl \
  -target=./local-gen-c \
  -emit=header \
  -out=./example.gen.h

Generate the implementation:

webrpc-gen \
  -schema=example.ridl \
  -target=./local-gen-c \
  -emit=impl \
  -header=example.gen.h \
  -out=./example.gen.c

When published as a gen-* module, this can also be used via:

webrpc-gen \
  -schema=example.ridl \
  -target=github.com/webrpc/gen-c@<version> \
  -emit=header \
  -out=./example.gen.h

or:

webrpc-gen \
  -schema=example.ridl \
  -target=github.com/webrpc/gen-c@<version> \
  -emit=impl \
  -header=example.gen.h \
  -out=./example.gen.c

Set Custom Template Variables

Change any of the following values by passing -option="Value" CLI flag to webrpc-gen.

webrpc-gen -option	Description	Default value	Version
-prefix=<name>	symbol and type prefix	schema name in snake_case	v0.0.1
-client	generate client declarations and runtime	true	v0.0.1
-emit=<mode>	emit either header or impl	header	v0.0.1
-header=<file>	header include used by impl output	<prefix>.h	v0.0.1

Notes

• -target can be a local template directory or a git module path.
• bigint support is string-based by design to avoid precision loss in C JSON handling.
• for precision-sensitive large integer values, prefer bigint over int64 / uint64 in the schema when targeting this generator
• The generated implementation is tested with smoke, codec, succinct, and reference interop coverage in this repo.