diff --git a/src/jsc/bindings/BunProcess.cpp b/src/jsc/bindings/BunProcess.cpp
index dd5b7bda072f..3e154b95c5de 100644
--- a/src/jsc/bindings/BunProcess.cpp
+++ b/src/jsc/bindings/BunProcess.cpp
@@ -171,12 +171,12 @@ namespace JSCastingHelpers = JSC::JSCastingHelpers;
 JSC_DECLARE_HOST_FUNCTION(Process_functionCwd);
 
 extern "C" uint8_t Bun__getExitCode(void*);
-extern "C" uint8_t Bun__setExitCode(void*, uint8_t);
-extern "C" bool Bun__closeChildIPC(JSGlobalObject*);
+extern "C" void Bun__setExitCode(void*, uint8_t);
+extern "C" void Bun__closeChildIPC(JSGlobalObject*);
 
 extern "C" bool Bun__GlobalObject__connectedIPC(JSGlobalObject*);
 extern "C" bool Bun__GlobalObject__hasIPC(JSGlobalObject*);
-extern "C" bool Bun__ensureProcessIPCInitialized(JSGlobalObject*);
+extern "C" void Bun__ensureProcessIPCInitialized(JSGlobalObject*);
 extern "C" const char* Bun__githubURL;
 extern "C" const char* Bun__sqlite3_version();
 BUN_DECLARE_HOST_FUNCTION(Bun__Process__send);
diff --git a/src/jsc/bindings/JSEnvironmentVariableMap.cpp b/src/jsc/bindings/JSEnvironmentVariableMap.cpp
index a67acad614b7..a6c8137751bb 100644
--- a/src/jsc/bindings/JSEnvironmentVariableMap.cpp
+++ b/src/jsc/bindings/JSEnvironmentVariableMap.cpp
@@ -352,9 +352,9 @@ bool JSEnvironmentVariableMap::deleteProperty(JSCell* cell, JSGlobalObject* glob
 }
 
 extern "C" int Bun__getTLSRejectUnauthorizedValue();
-extern "C" int Bun__setTLSRejectUnauthorizedValue(int value);
+extern "C" void Bun__setTLSRejectUnauthorizedValue(int value);
 extern "C" int Bun__getVerboseFetchValue();
-extern "C" int Bun__setVerboseFetchValue(int value);
+extern "C" void Bun__setVerboseFetchValue(int value);
 
 ALWAYS_INLINE static Identifier NODE_TLS_REJECT_UNAUTHORIZED_PRIVATE_PROPERTY(VM& vm)
 {
diff --git a/src/jsc/bindings/ZigSourceProvider.cpp b/src/jsc/bindings/ZigSourceProvider.cpp
index 50074091373e..8729da46df75 100644
--- a/src/jsc/bindings/ZigSourceProvider.cpp
+++ b/src/jsc/bindings/ZigSourceProvider.cpp
@@ -40,7 +40,7 @@ SourceOrigin toSourceOrigin(const String& sourceURL, bool isBuiltin)
     return SourceOrigin(WTF::URL::fileURLWithFileSystemPath(sourceURL));
 }
 
-extern "C" int ByteRangeMapping__getSourceID(void* mappings, BunString sourceURL);
+extern "C" int ByteRangeMapping__getSourceID(void* mappings);
 extern "C" void* ByteRangeMapping__find(BunString sourceURL);
 
 extern "C" void ByteRangeMapping__generate(BunString sourceURL, BunString code, int sourceID);
@@ -52,7 +52,7 @@ JSC::SourceID sourceIDForSourceURL(const WTF::String& sourceURL)
         return 0;
     }
 
-    return ByteRangeMapping__getSourceID(mappings, Bun::toString(sourceURL));
+    return ByteRangeMapping__getSourceID(mappings);
 }
 
 extern "C" bool BunTest__shouldGenerateCodeCoverage(BunString sourceURL);
diff --git a/src/jsc/bindings/bindings.cpp b/src/jsc/bindings/bindings.cpp
index 522e323496ad..6e52ea27f96e 100644
--- a/src/jsc/bindings/bindings.cpp
+++ b/src/jsc/bindings/bindings.cpp
@@ -5966,15 +5966,12 @@ extern "C" void WebCore__AbortSignal__decrementPendingActivity(WebCore::AbortSig
     abortSignal->decrementPendingActivityCount();
 }
 
-extern "C" WebCore::AbortSignal* WebCore__AbortSignal__signal(WebCore::AbortSignal* arg0, JSC::JSGlobalObject* globalObject, uint8_t reason)
+extern "C" void WebCore__AbortSignal__signal(WebCore::AbortSignal* arg0, JSC::JSGlobalObject* globalObject, uint8_t reason)
 {
-
     WebCore::AbortSignal* abortSignal = reinterpret_cast<WebCore::AbortSignal*>(arg0);
     abortSignal->signalAbort(
         globalObject,
         static_cast<WebCore::CommonAbortReason>(reason));
-    ;
-    return arg0;
 }
 
 extern "C" JSC::EncodedJSValue WebCore__AbortSignal__reasonIfAborted(WebCore::AbortSignal* signal, JSC::JSGlobalObject* globalObject, CommonAbortReason* reason)
diff --git a/src/jsc/bindings/headers.h b/src/jsc/bindings/headers.h
index 5c1acc4bf937..8c1f1f6a1ffd 100644
--- a/src/jsc/bindings/headers.h
+++ b/src/jsc/bindings/headers.h
@@ -124,7 +124,7 @@ CPP_DECL void WebCore__AbortSignal__cleanNativeBindings(WebCore::AbortSignal* ar
 CPP_DECL JSC::EncodedJSValue WebCore__AbortSignal__create(JSC::JSGlobalObject* arg0);
 CPP_DECL WebCore::AbortSignal* WebCore__AbortSignal__fromJS(JSC::EncodedJSValue JSValue0);
 CPP_DECL WebCore::AbortSignal* WebCore__AbortSignal__ref(WebCore::AbortSignal* arg0);
-CPP_DECL WebCore::AbortSignal* WebCore__AbortSignal__signal(WebCore::AbortSignal* arg0, JSC::JSGlobalObject*,  uint8_t abortReason);
+CPP_DECL void WebCore__AbortSignal__signal(WebCore::AbortSignal* arg0, JSC::JSGlobalObject*, uint8_t abortReason);
 CPP_DECL JSC::EncodedJSValue WebCore__AbortSignal__toJS(WebCore::AbortSignal* arg0, JSC::JSGlobalObject* arg1);
 CPP_DECL void WebCore__AbortSignal__unref(WebCore::AbortSignal* arg0);
 
diff --git a/src/jsc/virtual_machine_exports.rs b/src/jsc/virtual_machine_exports.rs
index c81f5f148d68..b44f9f4758fc 100644
--- a/src/jsc/virtual_machine_exports.rs
+++ b/src/jsc/virtual_machine_exports.rs
@@ -72,7 +72,7 @@ pub fn is_bun_main(global: &JSGlobalObject, str: &BunString) -> bool {
 }
 
 // HOST_EXPORT(Bun__reportUnhandledError, c)
-pub fn report_unhandled_error(global: &JSGlobalObject, value: JSValue) -> JSValue {
+pub fn report_unhandled_error(global: &JSGlobalObject, value: JSValue) {
     crate::mark_binding!();
 
     if !value.is_termination_exception() {
@@ -81,7 +81,6 @@ pub fn report_unhandled_error(global: &JSGlobalObject, value: JSValue) -> JSValu
             .as_mut()
             .uncaught_exception(global, value, false);
     }
-    JSValue::UNDEFINED
 }
 
 /// `ScriptExecutionContext::postTask` — the context addresses the thread's VM
diff --git a/src/runtime/ffi/ffi_body.rs b/src/runtime/ffi/ffi_body.rs
index 51d33c2b9a42..e64f2e8830f4 100644
--- a/src/runtime/ffi/ffi_body.rs
+++ b/src/runtime/ffi/ffi_body.rs
@@ -318,15 +318,16 @@ impl Source {
 mod stdarg {
     use super::*;
 
+    // Defined in c-bindings.cpp; `ap` is a `va_list`.
     unsafe extern "C" {
-        pub(super) fn ffi_vfprintf(_: *mut c_void, _: *const c_char, ...) -> c_int;
-        pub(super) fn ffi_vprintf(_: *const c_char, ...) -> c_int;
+        pub(super) fn ffi_vfprintf(_: *mut c_void, _: *const c_char, ap: *mut c_void) -> c_int;
+        pub(super) fn ffi_vprintf(_: *const c_char, ap: *mut c_void) -> c_int;
         pub(super) fn ffi_fprintf(_: *mut c_void, _: *const c_char, ...) -> c_int;
         pub(super) fn ffi_printf(_: *const c_char, ...) -> c_int;
         pub(super) fn ffi_fscanf(_: *mut c_void, _: *const c_char, ...) -> c_int;
         pub(super) fn ffi_scanf(_: *const c_char, ...) -> c_int;
         pub(super) fn ffi_sscanf(_: *const c_char, _: *const c_char, ...) -> c_int;
-        pub(super) fn ffi_vsscanf(_: *const c_char, _: *const c_char, ...) -> c_int;
+        pub(super) fn ffi_vsscanf(_: *const c_char, _: *const c_char, ap: *mut c_void) -> c_int;
         pub(super) fn ffi_fopen(_: *const c_char, _: *const c_char) -> *mut c_void;
         pub(super) fn ffi_fclose(_: *mut c_void) -> c_int;
         pub(super) fn ffi_fgetc(_: *mut c_void) -> c_int;
diff --git a/src/runtime/test_runner/expect.rs b/src/runtime/test_runner/expect.rs
index e7b3471e39c0..3f551ac9a85b 100644
--- a/src/runtime/test_runner/expect.rs
+++ b/src/runtime/test_runner/expect.rs
@@ -1427,7 +1427,6 @@ impl Expect {
                         &raw const matcher_name,
                         host_fn_ptr,
                         matcher_fn,
-                        true,
                     )
                 };
 
@@ -3257,7 +3256,6 @@ unsafe extern "C" {
         // Rust's `JSHostFn` is already the pointer type, so no extra `*const`.
         function_pointer: bun_jsc::JSHostFn,
         wrapped_fn: JSValue,
-        strong: bool,
     ) -> JSValue;
     fn Bun__JSWrappingFunction__getWrappedFunction(this: JSValue, global_this: *const JSGlobalObject) -> JSValue;
 
diff --git a/src/url/lib.rs b/src/url/lib.rs
index 94860e3f1070..75de0ac4d2b4 100644
--- a/src/url/lib.rs
+++ b/src/url/lib.rs
@@ -71,7 +71,7 @@ pub mod whatwg {
         safe fn URL__getFileURLString(input: &mut String) -> String;
         safe fn URL__getHrefJoin(base: &mut String, relative: &mut String) -> String;
         safe fn URL__fragmentIdentifier(url: &URL) -> String;
-        fn URL__originLength(latin1_slice: *const u8, len: usize) -> u32;
+        fn URL__originLength(latin1_slice: *const u8, len: usize) -> usize;
     }
 
     // The C ABI wants a mutable address. We take `&String` (matching existing call sites
@@ -106,7 +106,7 @@ pub mod whatwg {
         // to hand C++ only the leading ASCII prefix (latin1-safe).
         let first_non_ascii = strings::first_non_ascii(slice).map_or(slice.len(), |i| i as usize);
         // SAFETY: ptr/len derived from a valid slice prefix; C++ only reads.
-        let len = unsafe { URL__originLength(slice.as_ptr(), first_non_ascii) } as usize;
+        let len = unsafe { URL__originLength(slice.as_ptr(), first_non_ascii) };
         if len == 0 || len > first_non_ascii {
             return None;
         }