[LLD] [MinGW] Output debug info by default, unless the -s parameter is passed

[smeenai]

lld-link will include debug info sections in the linked binary if you pass -debug (and you probably also want to pass -nopdb to prevent PDB emission if you're using DWARF). Perhaps you should make the MinGW driver pass those two options by default and then not pass them if -s is passed to it?

[ruiu]

I think it does if your object file contains .debug_ sections, as Shoaib pointed out.

[rnk]

Assuming we're still committed to the translation layer approach, it sounds like we will need a /debug:dwarf flag or something similar to enable this behavior in a more sensible way. /debug /nopdb is a surprising spelling for "I want DWARF in my image".

[mstorsjo]

Output debug info by default.

Not sure whether it actually works though, because the gdb version I have (which is a tad old admittedly) refuses to load the lld produced exe, saying "not in executable format: File format not recognized". Although maybe the dwarf debug info does work with some other tools?

[ruiu]

COFF/Options.td

74 ↗

(On Diff #121381)

Move this to below "LLD extensions" comment in this file.

MinGW/Options.td

27 ↗

(On Diff #121381)

Can you define --strip-all as a primary option and define -s as an alias to it, in order to avoid cryptic variable name OPT_s?

[mstorsjo]

Moved the COFF option, made --strip-all the main option and -s an alias.

[ruiu]

LGTM

MinGW/Options.td

27 ↗

(On Diff #121381)

I think you want to use F instead of Flags because both -strip-all and --strip-all are valid.

lld/trunk/COFF/Driver.cpp

if (Args.hasArg(OPT_verbose))
     Config->Verbose = true;
   errorHandler().Verbose = Config->Verbose;
 
   // Handle /force or /force:unresolved
   if (Args.hasArg(OPT_force) || Args.hasArg(OPT_force_unresolved))
     Config->Force = true;
 
   // Handle /debug
-  if (Args.hasArg(OPT_debug)) {
+  if (Args.hasArg(OPT_debug) || Args.hasArg(OPT_debug_dwarf)) {
     Config->Debug = true;
     if (auto *Arg = Args.getLastArg(OPT_debugtype))
       Config->DebugTypes = parseDebugType(Arg->getValue());
     else
       Config->DebugTypes = getDefaultDebugType(Args);
   }
 
   // Create a dummy PDB file to satisfy build sytem rules.
void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
 
   // Put the PDB next to the image if no /pdb flag was passed.
   if (Config->Debug && Config->PDBPath.empty()) {
     Config->PDBPath = Config->OutputFile;
     sys::path::replace_extension(Config->PDBPath, ".pdb");
   }
 
   // Disable PDB generation if the user requested it.
-  if (Args.hasArg(OPT_nopdb))
+  if (Args.hasArg(OPT_nopdb) || Args.hasArg(OPT_debug_dwarf))
     Config->PDBPath = "";
 
   // Set default image base if /base is not given.
   if (Config->ImageBase == uint64_t(-1))
     Config->ImageBase = getDefaultImageBase();
 
   Symtab->addSynthetic(mangle("__ImageBase"), nullptr);
   if (Config->Machine == I386) {

lld/trunk/COFF/Options.td

 defm tsaware  : B<"tsaware",
                   "Create Terminal Server aware executable (default)",
                   "Create non-Terminal Server aware executable">;
 
 def help : F<"help">;
 def help_q : Flag<["/?", "-?"], "">, Alias<help>;
 
 // LLD extensions
+def debug_dwarf : F<"debug:dwarf">;
 def export_all_symbols : F<"export-all-symbols">;
 def nopdb : F<"nopdb">, HelpText<"Disable PDB generation for DWARF users">;
 def nosymtab : F<"nosymtab">;
 def lldmingw : F<"lldmingw">;
 def msvclto : F<"msvclto">;
 def output_def : Joined<["/", "-"], "output-def:">;
 def rsp_quoting : Joined<["--"], "rsp-quoting=">,
   HelpText<"Quoting style for response files, 'windows' (default) or 'posix'">;

lld/trunk/MinGW/Driver.cpp

else
     Add("-out:a.exe");
 
   if (Args.hasArg(OPT_shared))
     Add("-dll");
   if (Args.hasArg(OPT_verbose))
     Add("-verbose");
   if (Args.hasArg(OPT_export_all_symbols))
     Add("-export-all-symbols");
+  if (!Args.hasArg(OPT_strip_all))
+    Add("-debug:dwarf");
 
   if (auto *A = Args.getLastArg(OPT_m)) {
     StringRef S = A->getValue();
     if (S == "i386pe")
       Add("-machine:x86");
     else if (S == "i386pep")
       Add("-machine:x64");
     else if (S == "thumb2pe")

lld/trunk/MinGW/Options.td

 def o: JoinedOrSeparate<["-"], "o">, MetaVarName<"<path>">,
   HelpText<"Path to file to write output">;
 def out_implib: Separate<["--"], "out-implib">, HelpText<"Import library name">;
 def out_implib_eq: Joined<["--"], "out-implib=">, Alias<out_implib>;
 def output_def: S<"output-def">, HelpText<"Output def file">;
 def shared: F<"shared">, HelpText<"Build a shared object">;
 def subs: S<"subsystem">, HelpText<"Specify subsystem">;
 def stack: S<"stack">;
+def strip_all: F<"strip-all">,
+    HelpText<"Omit all symbol information from the output binary">;
 def whole_archive: F<"whole-archive">,
     HelpText<"Include all object files for following archives">;
 def verbose: F<"verbose">, HelpText<"Verbose mode">;
 
 // LLD specific options
 def _HASH_HASH_HASH : Flag<["-"], "###">,
     HelpText<"Print (but do not run) the commands to run for this compilation">;
 def mllvm: S<"mllvm">;

 def major_image_version: S<"major-image-version">;
 def minor_image_version: S<"minor-image-version">;
 def sysroot: J<"sysroot">, HelpText<"Sysroot">;
 def v: Flag<["-"], "v">, HelpText<"Display the version number">;
 def version: F<"version">, HelpText<"Display the version number and exit">;
 
 // Alias
 def alias_entry_e: JoinedOrSeparate<["-"], "e">, Alias<entry>;
+def alias_strip_s: Flag<["-"], "s">, Alias<strip_all>;

lld/trunk/test/MinGW/driver.test

 RUN: ld.lld -### -m i386pep foo.o --export-all-symbols | FileCheck -check-prefix EXPORT-ALL %s
 EXPORT-ALL: -export-all-symbols
 
 RUN: ld.lld -### -m i386pep foo.o --output-def out.def | FileCheck -check-prefix OUTPUT-DEF %s
 OUTPUT-DEF: -output-def:out.def
 
 RUN: ld.lld -### -m i386pep foo.o -Xlink=-lldmap | FileCheck -check-prefix XLINK %s
 XLINK: -lldmap
+
+RUN: ld.lld -### -m i386pep foo.o | FileCheck -check-prefix DEBUG %s
+DEBUG: -debug:dwarf
+
+RUN: ld.lld -### -m i386pep foo.o -s | FileCheck -check-prefix STRIP %s
+RUN: ld.lld -### -m i386pep foo.o --strip-all | FileCheck -check-prefix STRIP %s
+STRIP-NOT: -debug:dwarf