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Handle null from LLVMRustGetSectionName #62460

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merged 2 commits into from
Jul 9, 2019
Merged

Handle null from LLVMRustGetSectionName #62460

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f5b3021
Handle null from LLVMRustGetSectionName
nitnelave Mar 27, 2019
076a5cd
format a bit
RalfJung Jun 24, 2019
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4 changes: 3 additions & 1 deletion src/librustc_codegen_llvm/llvm/ffi.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1736,7 +1736,9 @@ extern "C" {
pub fn LLVMRustArchiveIteratorFree(AIR: &'a mut ArchiveIterator<'a>);
pub fn LLVMRustDestroyArchive(AR: &'static mut Archive);

pub fn LLVMRustGetSectionName(SI: &SectionIterator<'_>, data: &mut *const c_char) -> size_t;
#[allow(improper_ctypes)]
pub fn LLVMRustGetSectionName(SI: &SectionIterator<'_>,
data: &mut Option<std::ptr::NonNull<c_char>>) -> size_t;

#[allow(improper_ctypes)]
pub fn LLVMRustWriteTwineToString(T: &Twine, s: &RustString);
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13 changes: 9 additions & 4 deletions src/librustc_codegen_llvm/metadata.rs
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Expand Up @@ -8,7 +8,6 @@ use rustc_data_structures::owning_ref::OwningRef;
use rustc_codegen_ssa::METADATA_FILENAME;

use std::path::Path;
use std::ptr;
use std::slice;
use rustc_fs_util::path_to_c_string;

Expand Down Expand Up @@ -67,10 +66,16 @@ fn search_meta_section<'a>(of: &'a ObjectFile,
unsafe {
let si = mk_section_iter(of.llof);
while llvm::LLVMIsSectionIteratorAtEnd(of.llof, si.llsi) == False {
let mut name_buf = ptr::null();
let mut name_buf = None;
let name_len = llvm::LLVMRustGetSectionName(si.llsi, &mut name_buf);
let name = slice::from_raw_parts(name_buf as *const u8, name_len as usize).to_vec();
let name = String::from_utf8(name).unwrap();
let name = name_buf.map_or(
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For the purposes of this code, sections without name can be skipped entirely. I'm also wondering why this code is creating a String rather than a str, it does not seem necessary.

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@RalfJung RalfJung Jul 7, 2019 •
edited
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Are you saying I should change something? I literally have no idea what the code here is doing, I'm afraid. @nitnelave just did the minimal thing to avoid NULL references.

String::new(), // We got a NULL ptr, ignore `name_len`.
|buf| String::from_utf8(
slice::from_raw_parts(buf.as_ptr() as *const u8,
name_len as usize)
.to_vec()
).unwrap()
);
debug!("get_metadata_section: name {}", name);
if read_metadata_section_name(target) == name {
let cbuf = llvm::LLVMGetSectionContents(si.llsi);
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