1 // .debug_gdb_scripts binary section.
5 use crate::builder::Builder;
6 use crate::common::CodegenCx;
7 use crate::value::Value;
8 use rustc_codegen_ssa::base::collect_debugger_visualizers_transitive;
9 use rustc_codegen_ssa::traits::*;
10 use rustc_hir::def_id::LOCAL_CRATE;
11 use rustc_middle::bug;
12 use rustc_session::config::{CrateType, DebugInfo};
14 use rustc_span::symbol::sym;
15 use rustc_span::DebuggerVisualizerType;
17 /// Inserts a side-effect free instruction sequence that makes sure that the
18 /// .debug_gdb_scripts global is referenced, so it isn't removed by the linker.
19 pub fn insert_reference_to_gdb_debug_scripts_section_global(bx: &mut Builder<'_, '_, '_>) {
20 if needs_gdb_debug_scripts_section(bx) {
21 let gdb_debug_scripts_section =
22 bx.const_bitcast(get_or_insert_gdb_debug_scripts_section_global(bx), bx.type_i8p());
23 // Load just the first byte as that's all that's necessary to force
24 // LLVM to keep around the reference to the global.
25 let volative_load_instruction = bx.volatile_load(bx.type_i8(), gdb_debug_scripts_section);
27 llvm::LLVMSetAlignment(volative_load_instruction, 1);
32 /// Allocates the global variable responsible for the .debug_gdb_scripts binary
34 pub fn get_or_insert_gdb_debug_scripts_section_global<'ll>(cx: &CodegenCx<'ll, '_>) -> &'ll Value {
35 let c_section_var_name = "__rustc_debug_gdb_scripts_section__\0";
36 let section_var_name = &c_section_var_name[..c_section_var_name.len() - 1];
39 unsafe { llvm::LLVMGetNamedGlobal(cx.llmod, c_section_var_name.as_ptr().cast()) };
41 section_var.unwrap_or_else(|| {
42 let section_name = b".debug_gdb_scripts\0";
43 let mut section_contents = Vec::new();
45 // Add the pretty printers for the standard library first.
46 section_contents.extend_from_slice(b"\x01gdb_load_rust_pretty_printers.py\0");
48 // Next, add the pretty printers that were specified via the `#[debugger_visualizer]` attribute.
49 let visualizers = collect_debugger_visualizers_transitive(
51 DebuggerVisualizerType::GdbPrettyPrinter,
53 let crate_name = cx.tcx.crate_name(LOCAL_CRATE);
54 for (index, visualizer) in visualizers.iter().enumerate() {
55 // The initial byte `4` instructs GDB that the following pretty printer
56 // is defined inline as opposed to in a standalone file.
57 section_contents.extend_from_slice(b"\x04");
58 let vis_name = format!("pretty-printer-{}-{}\n", crate_name, index);
59 section_contents.extend_from_slice(vis_name.as_bytes());
60 section_contents.extend_from_slice(&visualizer.src);
62 // The final byte `0` tells GDB that the pretty printer has been
63 // fully defined and can continue searching for additional
65 section_contents.extend_from_slice(b"\0");
69 let section_contents = section_contents.as_slice();
70 let llvm_type = cx.type_array(cx.type_i8(), section_contents.len() as u64);
73 .define_global(section_var_name, llvm_type)
74 .unwrap_or_else(|| bug!("symbol `{}` is already defined", section_var_name));
75 llvm::LLVMSetSection(section_var, section_name.as_ptr().cast());
76 llvm::LLVMSetInitializer(section_var, cx.const_bytes(section_contents));
77 llvm::LLVMSetGlobalConstant(section_var, llvm::True);
78 llvm::LLVMSetUnnamedAddress(section_var, llvm::UnnamedAddr::Global);
79 llvm::LLVMRustSetLinkage(section_var, llvm::Linkage::LinkOnceODRLinkage);
80 // This should make sure that the whole section is not larger than
81 // the string it contains. Otherwise we get a warning from GDB.
82 llvm::LLVMSetAlignment(section_var, 1);
88 pub fn needs_gdb_debug_scripts_section(cx: &CodegenCx<'_, '_>) -> bool {
89 let omit_gdb_pretty_printer_section =
90 cx.tcx.sess.contains_name(cx.tcx.hir().krate_attrs(), sym::omit_gdb_pretty_printer_section);
92 // To ensure the section `__rustc_debug_gdb_scripts_section__` will not create
93 // ODR violations at link time, this section will not be emitted for rlibs since
94 // each rlib could produce a different set of visualizers that would be embedded
95 // in the `.debug_gdb_scripts` section. For that reason, we make sure that the
96 // section is only emitted for leaf crates.
97 let embed_visualizers = cx.sess().crate_types().iter().any(|&crate_type| match crate_type {
98 CrateType::Executable | CrateType::Dylib | CrateType::Cdylib | CrateType::Staticlib => {
99 // These are crate types for which we will embed pretty printers since they
100 // are treated as leaf crates.
103 CrateType::ProcMacro => {
104 // We could embed pretty printers for proc macro crates too but it does not
105 // seem like a good default, since this is a rare use case and we don't
106 // want to slow down the common case.
110 // As per the above description, embedding pretty printers for rlibs could
111 // lead to ODR violations so we skip this crate type as well.
116 !omit_gdb_pretty_printer_section
117 && cx.sess().opts.debuginfo != DebugInfo::None
118 && cx.sess().target.emit_debug_gdb_scripts