From eb4ce05bd00c89a99f859e391c6ab67f8e07cc38 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Mon, 23 Oct 2023 15:19:03 -0700
Subject: [PATCH] Restructure building the C API

This commit introduces a wrapper crate which is now the new "real" C
API. The purpose of this change is to enable using LTO when building the
C API. Currently LTO is disabled because one of the crate types of the C
API is an "rlib" which means that it can't have LTO performed due to
rustc limitations. The solution here is to remove the "cdylib" and
"staticlib" crate types from the "wasmtime-c-api" crate, rename that
crate to "wasmtime-c-api-impl", and reintroduce 'wasmtime-c-api' as a
new crate which wraps the previous crate and reexports it.

This way LTO can be enabled when just building the artifacts and the use
case from #6765 is still satisfied by having a crate that can be linked
to from Rust. Locally this reduces the size of the C API artifact for me
by nearly 1M.
---
 Cargo.lock                       |  7 ++++++
 Cargo.toml                       |  2 +-
 crates/c-api/CMakeLists.txt      |  4 +--
 crates/c-api/Cargo.toml          | 15 ++----------
 crates/c-api/artifact/Cargo.toml | 42 ++++++++++++++++++++++++++++++++
 crates/c-api/artifact/src/lib.rs |  1 +
 6 files changed, 55 insertions(+), 16 deletions(-)
 create mode 100644 crates/c-api/artifact/Cargo.toml
 create mode 100644 crates/c-api/artifact/src/lib.rs

diff --git a/Cargo.lock b/Cargo.lock
index 9399c8538603..43c3d10892b7 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3323,6 +3323,13 @@ dependencies = [
 [[package]]
 name = "wasmtime-c-api"
 version = "15.0.0"
+dependencies = [
+ "wasmtime-c-api-impl",
+]
+
+[[package]]
+name = "wasmtime-c-api-impl"
+version = "15.0.0"
 dependencies = [
  "anyhow",
  "cap-std",
diff --git a/Cargo.toml b/Cargo.toml
index b2b3f3b3cb7e..9b612a34f2a0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -101,7 +101,7 @@ members = [
   "cranelift/isle/islec",
   "cranelift/serde",
   "crates/bench-api",
-  "crates/c-api",
+  "crates/c-api/artifact",
   "crates/environ/fuzz",
   "crates/test-programs",
   "crates/wasi-preview1-component-adapter",
diff --git a/crates/c-api/CMakeLists.txt b/crates/c-api/CMakeLists.txt
index 782a9aa78b06..b5fb5e085f08 100644
--- a/crates/c-api/CMakeLists.txt
+++ b/crates/c-api/CMakeLists.txt
@@ -100,7 +100,7 @@ ExternalProject_Add(
 	CONFIGURE_COMMAND ""
 	INSTALL_COMMAND "${WASMTIME_INSTALL_COMMAND}"
         BUILD_COMMAND ${WASMTIME_PREBUILD_COMMAND} ${WASMTIME_CARGO_BINARY} build ${WASMTIME_BUILD_TYPE_FLAG} ${WASMTIME_USER_CARGO_BUILD_OPTIONS} ${WASMTIME_BUILD_TARGET}
-	BINARY_DIR ${CMAKE_CURRENT_SOURCE_DIR}
+	BINARY_DIR ${CMAKE_CURRENT_SOURCE_DIR}/artifact
         BUILD_ALWAYS ${WASMTIME_ALWAYS_BUILD}
 	BUILD_BYPRODUCTS ${WASMTIME_BUILD_PRODUCT})
 add_library(wasmtime INTERFACE)
@@ -137,5 +137,5 @@ install(FILES ${CMAKE_CURRENT_SOURCE_DIR}/wasm-c-api/include/wasm.h
 	DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 install(DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/include/wasmtime
 	DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
-install(FILES ${WASMTIME_BUILD_PRODUCT} 
+install(FILES ${WASMTIME_BUILD_PRODUCT}
 	DESTINATION ${CMAKE_INSTALL_LIBDIR})
diff --git a/crates/c-api/Cargo.toml b/crates/c-api/Cargo.toml
index 1548b0634dca..82d46337bba9 100644
--- a/crates/c-api/Cargo.toml
+++ b/crates/c-api/Cargo.toml
@@ -1,5 +1,5 @@
 [package]
-name = "wasmtime-c-api"
+name = "wasmtime-c-api-impl"
 version.workspace = true
 authors.workspace = true
 description = "C API to expose the Wasmtime runtime"
@@ -10,8 +10,7 @@ edition.workspace = true
 publish = false
 
 [lib]
-name = "wasmtime"
-crate-type = ["staticlib", "cdylib", "rlib"]
+name = "wamstime_c_api"
 doc = false
 test = false
 doctest = false
@@ -38,16 +37,6 @@ wasi-common = { workspace = true, optional = true }
 futures = { workspace = true, optional = true }
 
 [features]
-default = [
-  'profiling',
-  'wat',
-  'wasi',
-  'cache',
-  'parallel-compilation',
-  'async',
-  'coredump',
-  'addr2line',
-]
 async = ['wasmtime/async', 'futures']
 profiling = ["wasmtime/profiling"]
 cache = ["wasmtime/cache"]
diff --git a/crates/c-api/artifact/Cargo.toml b/crates/c-api/artifact/Cargo.toml
new file mode 100644
index 000000000000..0738a9df1dc0
--- /dev/null
+++ b/crates/c-api/artifact/Cargo.toml
@@ -0,0 +1,42 @@
+[package]
+name = "wasmtime-c-api"
+version.workspace = true
+authors.workspace = true
+description = "C API to expose the Wasmtime runtime"
+license = "Apache-2.0 WITH LLVM-exception"
+repository = "https://github.com/bytecodealliance/wasmtime"
+readme = "README.md"
+edition.workspace = true
+publish = false
+
+[lib]
+name = "wasmtime"
+crate-type = ["staticlib", "cdylib"]
+doc = false
+test = false
+doctest = false
+
+[dependencies]
+wasmtime-c-api = { path = '..', package = 'wasmtime-c-api-impl' }
+
+[features]
+default = [
+  'profiling',
+  'wat',
+  'wasi',
+  'cache',
+  'parallel-compilation',
+  'async',
+  'coredump',
+  'addr2line',
+]
+async = ['wasmtime-c-api/async']
+profiling = ["wasmtime-c-api/profiling"]
+cache = ["wasmtime-c-api/cache"]
+parallel-compilation = ['wasmtime-c-api/parallel-compilation']
+wasi = ['wasmtime-c-api/wasi']
+logging = ['wasmtime-c-api/logging']
+disable-logging = ["wasmtime-c-api/disable-logging"]
+coredump = ["wasmtime-c-api/coredump"]
+addr2line = ["wasmtime-c-api/addr2line"]
+wat = ["wasmtime-c-api/wat"]
diff --git a/crates/c-api/artifact/src/lib.rs b/crates/c-api/artifact/src/lib.rs
new file mode 100644
index 000000000000..43929bb8605f
--- /dev/null
+++ b/crates/c-api/artifact/src/lib.rs
@@ -0,0 +1 @@
+pub use wasmtime_c_api::*;