Rollup merge of #132340 - Zalathar:set-section, r=compiler-errors

cg_llvm: Consistently use safe wrapper function `set_section`

Follow-up to #131962 and https://github.com/rust-lang/rust/pull/132260#discussion_r1821626260.

To avoid too much scope creep, I've deliberately kept the changes to `LLVMRustGetSliceFromObjectDataByName` as minimal as possible.

compiler/rustc_codegen_llvm/src/back/lto.rs

@@ -165,13 +165,14 @@ fn get_bitcode_slice_from_object_data<'a>(
     // We drop the "__LLVM," prefix here because on Apple platforms there's a notion of "segment
     // name" which in the public API for sections gets treated as part of the section name, but
     // internally in MachOObjectFile.cpp gets treated separately.
-    let section_name = bitcode_section_name(cgcx).trim_start_matches("__LLVM,");
+    let section_name = bitcode_section_name(cgcx).to_str().unwrap().trim_start_matches("__LLVM,");
     let mut len = 0;
     let data = unsafe {
         llvm::LLVMRustGetSliceFromObjectDataByName(
             obj.as_ptr(),
             obj.len(),
             section_name.as_ptr(),
+            section_name.len(),
             &mut len,
         )
     };

compiler/rustc_codegen_llvm/src/back/write.rs

@@ -1,4 +1,4 @@
-use std::ffi::CString;
+use std::ffi::{CStr, CString};
 use std::io::{self, Write};
 use std::path::{Path, PathBuf};
 use std::sync::Arc;
@@ -958,14 +958,13 @@ fn target_is_aix(cgcx: &CodegenContext<LlvmCodegenBackend>) -> bool {
     cgcx.opts.target_triple.triple().contains("-aix")
 }
 
-//FIXME use c string literals here too
+pub(crate) fn bitcode_section_name(cgcx: &CodegenContext<LlvmCodegenBackend>) -> &'static CStr {
-pub(crate) fn bitcode_section_name(cgcx: &CodegenContext<LlvmCodegenBackend>) -> &'static str {
     if target_is_apple(cgcx) {
-        "__LLVM,__bitcode\0"
+        c"__LLVM,__bitcode"
     } else if target_is_aix(cgcx) {
-        ".ipa\0"
+        c".ipa"
     } else {
-        ".llvmbc\0"
+        c".llvmbc"
     }
 }
 
@@ -1042,8 +1041,7 @@ unsafe fn embed_bitcode(
             );
             llvm::LLVMSetInitializer(llglobal, llconst);
 
-            let section = bitcode_section_name(cgcx);
+            llvm::set_section(llglobal, bitcode_section_name(cgcx));
-            llvm::LLVMSetSection(llglobal, section.as_c_char_ptr());
             llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
             llvm::LLVMSetGlobalConstant(llglobal, llvm::True);
 
@@ -1061,7 +1059,7 @@ unsafe fn embed_bitcode(
             } else {
                 c".llvmcmd"
             };
-            llvm::LLVMSetSection(llglobal, section.as_ptr());
+            llvm::set_section(llglobal, section);
             llvm::set_linkage(llglobal, llvm::Linkage::PrivateLinkage);
         } else {
             // We need custom section flags, so emit module-level inline assembly.

compiler/rustc_codegen_llvm/src/base.rs

@@ -145,10 +145,8 @@ fn module_codegen(tcx: TyCtxt<'_>, cgu_name: Symbol) -> ModuleCodegen<ModuleLlvm
 
 pub(crate) fn set_link_section(llval: &Value, attrs: &CodegenFnAttrs) {
     let Some(sect) = attrs.link_section else { return };
-    unsafe {
+    let buf = SmallCStr::new(sect.as_str());
-        let buf = SmallCStr::new(sect.as_str());
+    llvm::set_section(llval, &buf);
-        llvm::LLVMSetSection(llval, buf.as_ptr());
-    }
 }
 
 pub(crate) fn linkage_to_llvm(linkage: Linkage) -> llvm::Linkage {

compiler/rustc_codegen_llvm/src/context.rs

@@ -565,7 +565,7 @@ pub(crate) fn create_used_variable_impl(&self, name: &'static CStr, values: &[&'
             let g = llvm::LLVMAddGlobal(self.llmod, self.val_ty(array), name.as_ptr());
             llvm::LLVMSetInitializer(g, array);
             llvm::set_linkage(g, llvm::Linkage::AppendingLinkage);
-            llvm::LLVMSetSection(g, c"llvm.metadata".as_ptr());
+            llvm::set_section(g, c"llvm.metadata");
         }
     }
 }

compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs

@@ -72,7 +72,7 @@ pub(crate) fn get_or_insert_gdb_debug_scripts_section_global<'ll>(
             let section_var = cx
                 .define_global(section_var_name, llvm_type)
                 .unwrap_or_else(|| bug!("symbol `{}` is already defined", section_var_name));
-            llvm::LLVMSetSection(section_var, c".debug_gdb_scripts".as_ptr());
+            llvm::set_section(section_var, c".debug_gdb_scripts");
             llvm::LLVMSetInitializer(section_var, cx.const_bytes(section_contents));
             llvm::LLVMSetGlobalConstant(section_var, llvm::True);
             llvm::LLVMSetUnnamedAddress(section_var, llvm::UnnamedAddr::Global);

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2416,6 +2416,7 @@ pub fn LLVMRustGetSliceFromObjectDataByName(
         data: *const u8,
         len: usize,
         name: *const u8,
+        name_len: usize,
         out_len: &mut usize,
     ) -> *const u8;
 

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -1559,8 +1559,10 @@ extern "C" LLVMModuleRef LLVMRustParseBitcodeForLTO(LLVMContextRef Context,
 extern "C" const char *LLVMRustGetSliceFromObjectDataByName(const char *data,
                                                             size_t len,
                                                             const char *name,
+                                                            size_t name_len,
                                                             size_t *out_len) {
   *out_len = 0;
+  auto Name = StringRef(name, name_len);
   auto Data = StringRef(data, len);
   auto Buffer = MemoryBufferRef(Data, ""); // The id is unused.
   file_magic Type = identify_magic(Buffer.getBuffer());
@@ -1571,8 +1573,8 @@ extern "C" const char *LLVMRustGetSliceFromObjectDataByName(const char *data,
     return nullptr;
   }
   for (const object::SectionRef &Sec : (*ObjFileOrError)->sections()) {
-    Expected<StringRef> Name = Sec.getName();
+    Expected<StringRef> SecName = Sec.getName();
-    if (Name && *Name == name) {
+    if (SecName && *SecName == Name) {
       Expected<StringRef> SectionOrError = Sec.getContents();
       if (!SectionOrError) {
         LLVMRustSetLastError(toString(SectionOrError.takeError()).c_str());