src/librustc_trans/trans/debuginfo/gdb.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // .debug_gdb_scripts binary section.
  12
  13 use llvm;
  14 use llvm::ValueRef;
  15
  16 use trans::common::{C_bytes, CrateContext};
  17 use trans::declare;
  18 use trans::type_::Type;
  19 use session::config::NoDebugInfo;
  20
  21 use std::ffi::CString;
  22 use std::ptr;
  23 use syntax::attr;
  24
  25
  26 /// Inserts a side-effect free instruction sequence that makes sure that the
  27 /// .debug_gdb_scripts global is referenced, so it isn't removed by the linker.
  28 pub fn insert_reference_to_gdb_debug_scripts_section_global(ccx: &CrateContext) {
  29     if needs_gdb_debug_scripts_section(ccx) {
  30         let empty = CString::new("").unwrap();
  31         let gdb_debug_scripts_section_global =
  32             get_or_insert_gdb_debug_scripts_section_global(ccx);
  33         unsafe {
  34             let volative_load_instruction =
  35                 llvm::LLVMBuildLoad(ccx.raw_builder(),
  36                                     gdb_debug_scripts_section_global,
  37                                     empty.as_ptr());
  38             llvm::LLVMSetVolatile(volative_load_instruction, llvm::True);
  39         }
  40     }
  41 }
  42
  43 /// Allocates the global variable responsible for the .debug_gdb_scripts binary
  44 /// section.
  45 pub fn get_or_insert_gdb_debug_scripts_section_global(ccx: &CrateContext)
  46                                                   -> llvm::ValueRef {
  47     let section_var_name = "__rustc_debug_gdb_scripts_section__";
  48
  49     let section_var = unsafe {
  50         llvm::LLVMGetNamedGlobal(ccx.llmod(),
  51                                  section_var_name.as_ptr() as *const _)
  52     };
  53
  54     if section_var == ptr::null_mut() {
  55         let section_name = b".debug_gdb_scripts\0";
  56         let section_contents = b"\x01gdb_load_rust_pretty_printers.py\0";
  57
  58         unsafe {
  59             let llvm_type = Type::array(&Type::i8(ccx),
  60                                         section_contents.len() as u64);
  61
  62             let section_var = declare::define_global(ccx, section_var_name,
  63                                                      llvm_type).unwrap_or_else(||{
  64                 ccx.sess().bug(&format!("symbol `{}` is already defined", section_var_name))
  65             });
  66             llvm::LLVMSetSection(section_var, section_name.as_ptr() as *const _);
  67             llvm::LLVMSetInitializer(section_var, C_bytes(ccx, section_contents));
  68             llvm::LLVMSetGlobalConstant(section_var, llvm::True);
  69             llvm::LLVMSetUnnamedAddr(section_var, llvm::True);
  70             llvm::SetLinkage(section_var, llvm::Linkage::LinkOnceODRLinkage);
  71             // This should make sure that the whole section is not larger than
  72             // the string it contains. Otherwise we get a warning from GDB.
  73             llvm::LLVMSetAlignment(section_var, 1);
  74             section_var
  75         }
  76     } else {
  77         section_var
  78     }
  79 }
  80
  81 pub fn needs_gdb_debug_scripts_section(ccx: &CrateContext) -> bool {
  82     let omit_gdb_pretty_printer_section =
  83         attr::contains_name(&ccx.tcx()
  84                                 .map
  85                                 .krate()
  86                                 .attrs,
  87                             "omit_gdb_pretty_printer_section");
  88
  89     !omit_gdb_pretty_printer_section &&
  90     !ccx.sess().target.target.options.is_like_osx &&
  91     !ccx.sess().target.target.options.is_like_windows &&
  92     ccx.sess().opts.debuginfo != NoDebugInfo
  93 }