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// .debug_gdb_scripts binary section.
use std::collections::BTreeSet;
use std::ffi::CString;
use rustc_codegen_ssa::traits::*;
use rustc_hir::def_id::LOCAL_CRATE;
use rustc_middle::bug;
use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerType;
use rustc_session::config::DebugInfo;
use crate::builder::Builder;
use crate::common::CodegenCx;
use crate::llvm;
use crate::value::Value;
/// Inserts a side-effect free instruction sequence that makes sure that the
/// .debug_gdb_scripts global is referenced, so it isn't removed by the linker.
pub(crate) fn insert_reference_to_gdb_debug_scripts_section_global(bx: &mut Builder<'_, '_, '_>) {
if needs_gdb_debug_scripts_section(bx) {
let gdb_debug_scripts_section = get_or_insert_gdb_debug_scripts_section_global(bx);
// Load just the first byte as that's all that's necessary to force
// LLVM to keep around the reference to the global.
let volatile_load_instruction = bx.volatile_load(bx.type_i8(), gdb_debug_scripts_section);
unsafe {
llvm::LLVMSetAlignment(volatile_load_instruction, 1);
}
}
}
/// Allocates the global variable responsible for the .debug_gdb_scripts binary
/// section.
pub(crate) fn get_or_insert_gdb_debug_scripts_section_global<'ll>(
cx: &CodegenCx<'ll, '_>,
) -> &'ll Value {
let c_section_var_name = CString::new(format!(
"__rustc_debug_gdb_scripts_section_{}_{:08x}",
cx.tcx.crate_name(LOCAL_CRATE),
cx.tcx.stable_crate_id(LOCAL_CRATE),
))
.unwrap();
let section_var_name = c_section_var_name.to_str().unwrap();
let section_var = unsafe { llvm::LLVMGetNamedGlobal(cx.llmod, c_section_var_name.as_ptr()) };
section_var.unwrap_or_else(|| {
let mut section_contents = Vec::new();
// Add the pretty printers for the standard library first.
section_contents.extend_from_slice(b"\x01gdb_load_rust_pretty_printers.py\0");
// Next, add the pretty printers that were specified via the `#[debugger_visualizer]`
// attribute.
let visualizers = cx
.tcx
.debugger_visualizers(LOCAL_CRATE)
.iter()
.filter(|visualizer| {
visualizer.visualizer_type == DebuggerVisualizerType::GdbPrettyPrinter
})
.collect::<BTreeSet<_>>();
let crate_name = cx.tcx.crate_name(LOCAL_CRATE);
for (index, visualizer) in visualizers.iter().enumerate() {
// The initial byte `4` instructs GDB that the following pretty printer
// is defined inline as opposed to in a standalone file.
section_contents.extend_from_slice(b"\x04");
let vis_name = format!("pretty-printer-{crate_name}-{index}\n");
section_contents.extend_from_slice(vis_name.as_bytes());
section_contents.extend_from_slice(&visualizer.src);
// The final byte `0` tells GDB that the pretty printer has been
// fully defined and can continue searching for additional
// pretty printers.
section_contents.extend_from_slice(b"\0");
}
unsafe {
let section_contents = section_contents.as_slice();
let llvm_type = cx.type_array(cx.type_i8(), section_contents.len() as u64);
let section_var = cx
.define_global(section_var_name, llvm_type)
.unwrap_or_else(|| bug!("symbol `{}` is already defined", section_var_name));
llvm::set_section(section_var, c".debug_gdb_scripts");
llvm::set_initializer(section_var, cx.const_bytes(section_contents));
llvm::LLVMSetGlobalConstant(section_var, llvm::True);
llvm::set_unnamed_address(section_var, llvm::UnnamedAddr::Global);
llvm::set_linkage(section_var, llvm::Linkage::LinkOnceODRLinkage);
// This should make sure that the whole section is not larger than
// the string it contains. Otherwise we get a warning from GDB.
llvm::LLVMSetAlignment(section_var, 1);
section_var
}
})
}
pub(crate) fn needs_gdb_debug_scripts_section(cx: &CodegenCx<'_, '_>) -> bool {
cx.sess().opts.debuginfo != DebugInfo::None && cx.sess().target.emit_debug_gdb_scripts
}
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