fix: remove the stub code

fuzz/Cargo.lock

@@ -2009,7 +2009,6 @@ dependencies = [
  "afl",
  "arbitrary",
  "borsh",
- "cc",
  "common",
  "fuzz_props",
  "libfuzzer-sys",

fuzz/Cargo.toml

@@ -3,8 +3,6 @@ name = "fuzz"
 version = "0.1.0"
 edition = "2024"
 publish = false
-# Provides sys_alloc_aligned stub for non-RISC-V host builds (see build.rs)
-build = "build.rs"
 
 [package.metadata]
 cargo-fuzz = true
@@ -52,10 +50,6 @@ common        = { path = "../../logos-execution-zone/common" }
 fuzz_props    = { path = "../fuzz_props" }
 testnet_initial_state = { path = "../../logos-execution-zone/testnet_initial_state" }
 
-[build-dependencies]
-# Used by build.rs to compile the sys_alloc_aligned stub for non-RISC-V hosts
-cc = "1"
-
 [profile.release]
 debug = true
 opt-level = 3

fuzz/build.rs

@@ -1,25 +0,0 @@
-// fuzz/build.rs
-//
-// Provides `sys_alloc_aligned` for non-RISC-V host targets.
-//
-// `risc0_zkvm_platform::syscall::sys_alloc_words` calls the bare-metal symbol
-// `sys_alloc_aligned`, which is normally supplied by the RISC-V zkVM runtime.
-// When compiling fuzz targets for a host target (x86_64-unknown-linux-gnu,
-// aarch64-unknown-linux-gnu, …) that symbol is absent, causing a linker error.
-// This build script compiles a small C stub via the `cc` crate so the symbol
-// is always available in the final fuzz binary.
-//
-// On macOS host builds (used by `cargo fuzz` / libFuzzer) the `cc` crate
-// compiles the same stub; it is harmlessly dead-stripped if the symbol is not
-// referenced.
-
-fn main() {
-    let target_arch = std::env::var("CARGO_CFG_TARGET_ARCH").unwrap_or_default();
-
-    // RISC-V builds get the real symbol from the zkVM runtime — skip the stub.
-    if target_arch != "riscv32" && target_arch != "riscv64" {
-        cc::Build::new()
-            .file("build_stubs/sys_alloc_aligned.c")
-            .compile("sys_alloc_stub");
-    }
-}

fuzz/build_stubs/sys_alloc_aligned.c

@@ -1,26 +0,0 @@
-/*
- * sys_alloc_aligned.c
- *
- * Provides `sys_alloc_aligned` for non-RISC-V host targets
- * (e.g. aarch64-unknown-linux-gnu, x86_64-unknown-linux-gnu).
- *
- * On RISC-V the real symbol is supplied by the zkVM bare-metal runtime.
- * On host targets, risc0_zkvm_platform may still reference this symbol via
- * its `sys_alloc_words` helper; this stub satisfies that reference using
- * POSIX `posix_memalign`.
- */
-#ifndef __riscv
-
-#include <stddef.h>
-#include <stdlib.h>
-
-void *sys_alloc_aligned(size_t bytes, size_t align) {
-    void *ptr = NULL;
-    /* posix_memalign requires alignment >= sizeof(void*) and a power of 2. */
-    size_t real_align = align < sizeof(void *) ? sizeof(void *) : align;
-    if (posix_memalign(&ptr, real_align, bytes) != 0)
-        return NULL;
-    return ptr;
-}
-
-#endif /* !__riscv */