feat: only call entrypoint in zkvm (#1611)

crates/zkvm/entrypoint/src/lib.rs

@@ -102,6 +102,14 @@ macro_rules! entrypoint {
 
             #[no_mangle]
             fn main() {
+                // Link to the actual entrypoint only when compiling for zkVM. Doing this avoids
+                // compilation errors when building for the host target.
+                //
+                // Note that, however, it's generally considered wasted effort compiling zkVM
+                // programs against the host target. This just makes it such that doing so wouldn't
+                // result in an error, which can happen when building a Cargo workspace containing
+                // zkVM program crates.
+                #[cfg(target_os = "zkvm")]
                 super::ZKVM_ENTRY()
             }
         }

examples/json/program/src/main.rs

@@ -4,7 +4,7 @@ sp1_zkvm::entrypoint!(main);
 use lib::{Account, Transaction}; // Custom structs.
 use serde_json::Value; // Generic JSON.
 
-fn main() {
+pub fn main() {
     // read generic JSON example inputs.
     let data_str = sp1_zkvm::io::read::<String>();
     let key = sp1_zkvm::io::read::<String>();

examples/patch-testing/program/src/main.rs

@@ -166,7 +166,7 @@ fn test_secp256k1_patch() {
 }
 
 /// To add testing for a new patch, add a new case to the function below.
-fn main() {
+pub fn main() {
     // TODO: Specify which syscalls are linked to each function invocation, iterate
     // over this list that is shared between the program and script.
     test_keccak();

examples/patch-testing/script/src/main.rs

@@ -3,7 +3,7 @@ use sp1_sdk::{utils, ProverClient, SP1Stdin};
 const PATCH_TEST_ELF: &[u8] = include_bytes!("../../program/elf/riscv32im-succinct-zkvm-elf");
 
 /// This script is used to test that SP1 patches are correctly applied and syscalls are triggered.
-fn main() {
+pub fn main() {
     utils::setup_logger();
 
     let stdin = SP1Stdin::new();

examples/ssz-withdrawals/program/src/main.rs

@@ -14,7 +14,7 @@ use hex_literal::hex;
 use ssz_rs::prelude::*;
 use std::collections::HashMap;
 
-fn main() {
+pub fn main() {
     // Get inputs.
     let beacon_block_root =
         node_from_bytes(hex!("d00c4da1a3ad4d42bd35f128544227d19e163194569d69d54a3d14112e3c897c"));

examples/tendermint/program/src/main.rs

@@ -6,7 +6,7 @@ use tendermint_light_client_verifier::{
     options::Options, types::LightBlock, ProdVerifier, Verdict, Verifier,
 };
 
-fn main() {
+pub fn main() {
     // Normally we could just do this to read in the LightBlocks, but bincode doesn't work with LightBlock.
     // This is likely a bug in tendermint-rs.
     // let light_block_1 = sp1_zkvm::io::read::<LightBlock>();

examples/tendermint/script/src/main.rs

@@ -19,7 +19,7 @@ fn get_light_blocks() -> (LightBlock, LightBlock) {
     (light_block_1, light_block_2)
 }
 
-fn main() {
+pub fn main() {
     // Generate proof.
     utils::setup_logger();
 

tests/tendermint-benchmark/src/main.rs

@@ -33,7 +33,7 @@ pub struct BlockValidatorSet {
     pub total: String,
 }
 
-fn main() {
+pub fn main() {
     let peer_id: [u8; 20] = [
         0x72, 0x6b, 0xc8, 0xd2, 0x60, 0x38, 0x7c, 0xf5, 0x6e, 0xcf, 0xad, 0x3a, 0x6b, 0xf6, 0xfe,
         0xcd, 0x90, 0x3e, 0x18, 0xa2,

tests/uint256-mul/src/main.rs

@@ -26,7 +26,7 @@ fn biguint_to_bytes_le(x: BigUint) -> [u8; 32] {
 }
 
 #[sp1_derive::cycle_tracker]
-fn main() {
+pub fn main() {
     for _ in 0..50 {
         // Test with random numbers.
         let mut rng = rand::thread_rng();