coverage: Don't convert symbol names to CString for FFI

Author: Zalathar

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -25,7 +25,6 @@ use rustc_middle::ty::Instance;
 use rustc_middle::ty::Ty;
 
 use std::cell::RefCell;
-use std::ffi::CString;
 
 pub(crate) mod ffi;
 pub(crate) mod map_data;
@@ -332,10 +331,15 @@ fn create_pgo_func_name_var<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     instance: Instance<'tcx>,
 ) -> &'ll llvm::Value {
-    let mangled_fn_name = CString::new(cx.tcx.symbol_name(instance).name)
-        .expect("error converting function name to C string");
+    let mangled_fn_name: &str = cx.tcx.symbol_name(instance).name;
     let llfn = cx.get_fn(instance);
-    unsafe { llvm::LLVMRustCoverageCreatePGOFuncNameVar(llfn, mangled_fn_name.as_ptr()) }
+    unsafe {
+        llvm::LLVMRustCoverageCreatePGOFuncNameVar(
+            llfn,
+            mangled_fn_name.as_ptr().cast(),
+            mangled_fn_name.len(),
+        )
+    }
 }
 
 pub(crate) fn write_filenames_section_to_buffer<'a>(

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1720,7 +1720,11 @@ extern "C" {
         BufferOut: &RustString,
     );
 
-    pub fn LLVMRustCoverageCreatePGOFuncNameVar(F: &Value, FuncName: *const c_char) -> &Value;
+    pub fn LLVMRustCoverageCreatePGOFuncNameVar(
+        F: &Value,
+        FuncName: *const c_char,
+        FuncNameLen: size_t,
+    ) -> &Value;
     pub fn LLVMRustCoverageHashByteArray(Bytes: *const c_char, NumBytes: size_t) -> u64;
 
     #[allow(improper_ctypes)]

compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp

@@ -161,8 +161,11 @@ extern "C" void LLVMRustCoverageWriteMappingToBuffer(
   CoverageMappingWriter.write(OS);
 }
 
-extern "C" LLVMValueRef LLVMRustCoverageCreatePGOFuncNameVar(LLVMValueRef F, const char *FuncName) {
-  StringRef FuncNameRef(FuncName);
+extern "C" LLVMValueRef LLVMRustCoverageCreatePGOFuncNameVar(
+    LLVMValueRef F,
+    const char *FuncName,
+    size_t FuncNameLen) {
+  StringRef FuncNameRef(FuncName, FuncNameLen);
   return wrap(createPGOFuncNameVar(*cast<Function>(unwrap(F)), FuncNameRef));
 }