Autogenerate C and Go wrappers

[qmuntal]

Until now we have been generating the C function headers. the C functions dlsym calls, and the C wrappers using good old C macros. C macros have the advantage of not needing to implement a parser for a new domain specific language (aka DSL) and to be pretty compact. On the other hand, they are difficult to troubleshoot if there is any issue with them, the error message is long and cryptic, and, most important, they have its limit on what can be sanely implemented with them.

This PR sets the ground for many improvements to come by dropping the C macro approach and instead use implement a small application (mkcgo) that can read C function definitions (limited to what is necessary to support OpenSSL) and then generates all the C stubs plus a handy Go wrappers over them.

This PR doesn't have any behavior change, it's only syntactic changes. It does add ~3000 line of code, but almost all of them are from autogenerated code.

[Copilot]

PR Overview

This PR replaces the legacy C macro-based wrapper generation with a dedicated mkcgo tool that reads C function definitions and automatically generates both C stubs and Go wrappers. Key changes include:

• Replacing direct C macro calls with calls to a set of go_openssl_* helper functions across multiple files.
• Migrating type definitions and function signatures from C types (e.g. C.int, C.size_t, C.GO_EVP_PKEY_PTR) to native Go types (e.g. int32, int) and wrapped pointer types (e.g. _EVP_PKEY_PTR).
• Updating supporting tools like checkheader and cgo directives to align with the new naming conventions.

Reviewed Changes

File	Description
cmd/checkheader/main.go	Updates output file handling and replaces hard-coded string with os.DevNull for better cross‑platform support.
const.go	Changes the return type of cString.ptr from *C.char to *byte, affecting downstream usage.
cgo_go124.go	Removes the go_openssl_ prefix from cgo directives to match updated naming conventions.
[various others]	Numerous files now use go_openssl_* wrappers and updated type conversions throughout the wrapper generation code.

Copilot reviewed 31 out of 31 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (3)

cmd/checkheader/main.go:95

• Using os.DevNull instead of a hard-coded "/dev/null" improves cross-platform compatibility. Please verify that similar improvements are applied consistently across the codebase.

"-o", os.DevNull, // discard output

const.go:23

• The function signature now returns *byte instead of *C.char. Ensure that all its call sites are updated to handle the new return type appropriately.

func (s cString) ptr() *byte {

cgo_go124.go:17

• [nitpick] The removal of the 'go_openssl_' prefix in the cgo directives affects the naming consistency with the rest of the code. Please double-check that the declarations and corresponding usage in Go match the updated naming convention.

#cgo noescape RAND_bytes

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[dagood]

For context, based on a conversation earlier, one of the major things this will make reasonable to implement is a good fix for:

• Error handling is not thead-safe #231

[Copilot]

PR Overview

This PR replaces the traditional C macro–based generation of wrappers with a small application that autogenerates both C stubs and Go wrappers. Key changes include replacing C type aliases with new Go‐defined types, removing dependency on legacy “goopenssl.h” comments, and updating cgo directives and function calls throughout the codebase.

Reviewed Changes

File	Description
cmd/mkcgo/main.go	Introduces the new mkcgo application for generating wrappers.
const.go	Updates pointer conversion from *C.char to *byte for C string data.
evp.go	Adjusts type conversions and key-generation function calls.
Other wrapper files	Transition from legacy C macros to explicit Go function calls.

Copilot reviewed 34 out of 34 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

const.go:30

• Switching the return type from *C.char to *byte may break compatibility with C functions that expect a null-terminated C string pointer. Please verify that all consumers of this pointer are updated accordingly to handle the new type while ensuring the string remains null-terminated.

return unsafe.StringData(string(s))

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[qmuntal]

I've upgraded the ubuntu CI agent to 22.04 as Ubuntu 20.04 is being sunsetted and in burnout period: actions/runner-images#11101

[dagood]

I looked a bit deeper at the changes throughout the library, but also a few more ideas about the generator. It looks like it would be fine to merge and start using, but I have some questions and ideas.

[dagood]

Hmm, could tidy up the syntax with #define TAG(X) __attribute__((tag(X))), #define VARIADIC(X) ..., etc. (both , and multiple __attribute__ seem to be valid.)

(Or really... #define TAG(X), because we aren't asking gcc to parse these for us anyway. 😄)