Add RISC0_ETHEREUM_PATH env to ffi

.gitignore

@@ -13,6 +13,7 @@ rust-project.json
 target/
 tmp/
 out/
+cache/
 
 # Ignore .pb files generated by profiling
 *.pb

build/src/lib.rs

@@ -53,6 +53,8 @@ const ELF_LIB_HEADER: &str = r#"pragma solidity ^0.8.20;
 library Elf {
 "#;
 
+const FFI_MANIFEST_PATH: &str = "ffi/Cargo.toml";
+
 /// Options for building and code generation.
 #[derive(Debug, Clone, Default)]
 #[non_exhaustive] // more options may be added in the future.
@@ -142,6 +144,25 @@ pub fn generate_elf_sol(guests: &[GuestListEntry]) -> Result<Vec<u8>> {
     forge_fmt(file_content.as_bytes()).context("failed to format image ID file")
 }
 
+/// Build risc0-ethereum forge ffi.
+pub fn build_ffi(risc0_ethereum_path: &str) -> Result<()> {
+    let ffi_path = Path::new(risc0_ethereum_path).join(FFI_MANIFEST_PATH);
+    let status = Command::new("cargo")
+        .arg("build")
+        .arg("--manifest-path")
+        .arg(ffi_path.as_os_str())
+        .arg("--bin")
+        .arg("risc0-forge-ffi")
+        .status()?;
+    if !status.success() {
+        bail!(
+            "risc0-ethereum forge ffi build failed with exit code: {:?}",
+            status.code()
+        )
+    }
+    Ok(())
+}
+
 /// Uses forge fmt as a subprocess to format the given Solidity source.
 fn forge_fmt(src: &[u8]) -> Result<Vec<u8>> {
     // Spawn `forge fmt`

contracts/src/test/RiscZeroCheats.sol

@@ -50,10 +50,11 @@ abstract contract RiscZeroCheats is CommonBase {
     function prove(string memory elf_path, bytes memory input) internal returns (bytes memory, bytes memory) {
         string[] memory imageRunnerInput = new string[](10);
         uint256 i = 0;
+        string memory risc0EthereumPath = vm.envOr("RISC0_ETHEREUM_PATH", string("lib/risc0-ethereum"));
         imageRunnerInput[i++] = "cargo";
         imageRunnerInput[i++] = "run";
         imageRunnerInput[i++] = "--manifest-path";
-        imageRunnerInput[i++] = "lib/risc0-ethereum/ffi/Cargo.toml";
+        imageRunnerInput[i++] = string.concat(risc0EthereumPath, "/ffi/Cargo.toml");
         imageRunnerInput[i++] = "--bin";
         imageRunnerInput[i++] = "risc0-forge-ffi";
         imageRunnerInput[i++] = "-q";

examples/erc20-counter/methods/build.rs

@@ -15,12 +15,14 @@
 use std::{collections::HashMap, env};
 
 use risc0_build::{embed_methods_with_options, DockerOptions, GuestOptions};
-use risc0_build_ethereum::generate_solidity_files;
+use risc0_build_ethereum::{build_ffi, generate_solidity_files};
 
 // Paths where the generated Solidity files will be written.
 const SOLIDITY_IMAGE_ID_PATH: &str = "../contracts/ImageID.sol";
 const SOLIDITY_ELF_PATH: &str = "../contracts/Elf.sol";
 
+const RISC0_ETHEREUM_PATH: &str = "../../..";
+
 fn main() {
     // Builds can be made deterministic, and thereby reproducible, by using Docker to build the
     // guest. Check the RISC0_USE_DOCKER variable and use Docker to build the guest if set.
@@ -43,4 +45,9 @@ fn main() {
         .with_elf_sol_path(SOLIDITY_ELF_PATH);
 
     generate_solidity_files(guests.as_slice(), &solidity_opts).unwrap();
+
+    // Build risc0-ethereum forge ffi.
+    let risc0_ethereum_path =
+        &env::var("RISC0_ETHEREUM_PATH").unwrap_or_else(|_| RISC0_ETHEREUM_PATH.to_string());
+    build_ffi(risc0_ethereum_path).unwrap();
 }