Resolve binary symlinks before finding its separate .debug file

[jankratochvil]

Summary

I have found LLDB cannot find separate debug info of Fedora /usr/bin/gdb. It is because:

lrwxrwxrwx 1 root root       14 Jan 25 20:41 /usr/bin/gdb -> ../libexec/gdb*
-rwxr-xr-x 1 root root 10180296 Jan 25 20:41 /usr/libexec/gdb*
ls: cannot access '/usr/lib/debug/usr/bin/gdb-8.0.1-35.fc27.x86_64.debug': No such file or directory
-r--r--r-- 1 root root 29200464 Jan 25 20:41 /usr/lib/debug/usr/libexec/gdb-8.0.1-35.fc27.x86_64.debug

FYI that -8.0.1-35.fc27.x86_64.debug may look confusing, it was always just .debug before.
Why is /usr/bin/gdb a symlink is offtopic for this bugreport, Fedora has it so for some reasons.

It is always safest to look at the .debug file only after resolving all symlinks on the binary file. I hope it should not cause any regressions.

[clayborg]

Makes sense for me, but make sure Pavel is ok with this as well before committing.

[jingham]

Can you fix the test case as mentioned inline. If something doesn't work please just ping me and I'll fix it. I'd like to get off propagating this boiler-plate...

packages/Python/lldbsuite/test/linux/sepdebugsymlink/TestSymbolsSepDebugSymlink.py

23–37 ↗

(On Diff #132621)

You should be able to do all this with the run_to_name_breakpoint. Pass "dirsymlink/stripped.symlink" as exe_name. I just added the ability to limit the breakpoint to a particular module, so you can do that as well.

Having all this duplicated boiler-plate made Adrian's laudable job of building out of tree way more tedious than it should have been. We should centralize this whenever possible.

[jankratochvil]

Simplify the testcase by: lldbutil.run_to_name_breakpoint

[labath]

Looks fine, just a couple of tweaks to the test case. No need to wait for another round of review.

packages/Python/lldbsuite/test/linux/sepdebugsymlink/TestTargetSymbolsSepDebugSymlink.py

17 ↗

(On Diff #132670)

source seems to be unused (and after that you can also remove the setUp function).

20 ↗

(On Diff #132670)

Please add something like skipIf(hostoslist=["windows"]) here. (The point being that the symlink creation will not work when doing remote debugging from windows).

lldb/trunk/packages/Python/lldbsuite/test/linux/sepdebugsymlink/Makefile

+LEVEL = ../../make
+C_SOURCES := main.c
+
+all: dirsymlink
+
+dirreal: a.out
+  $(RM) -r $@
+  mkdir $@
+  $(OBJCOPY) --only-keep-debug $< $@/stripped.debug
+  $(OBJCOPY) --strip-all --add-gnu-debuglink=$@/stripped.debug $< $@/stripped.out
+
+dirsymlink: dirreal
+  $(RM) -r $@
+  mkdir $@
+  ln -s ../$</stripped.out $@/stripped.symlink
+
+clean::
+  $(RM) -r dirreal dirsymlink
+
+include $(LEVEL)/Makefile.rules

lldb/trunk/packages/Python/lldbsuite/test/linux/sepdebugsymlink/TestTargetSymbolsSepDebugSymlink.py

+""" Testing separate debug info loading for base binary with a symlink. """
+import os
+import time
+import lldb
+import sys
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestTargetSymbolsSepDebugSymlink(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @no_debug_info_test  # Prevent the genaration of the dwarf version of this test
+    @skipUnlessPlatform(['linux'])
+    @skipIf(hostoslist=["windows"])
+    def test_target_symbols_sepdebug_symlink_case(self):
+        self.build(clean=True)
+        exe = self.getBuildArtifact("dirsymlink/stripped.symlink")
+
+        lldbutil.run_to_name_breakpoint(self, "main", exe_name = exe)

lldb/trunk/packages/Python/lldbsuite/test/linux/sepdebugsymlink/main.c

+int main() {
+  return 0;
+}

lldb/trunk/source/Host/common/Symbols.cpp

 //===-- Symbols.cpp ---------------------------------------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Host/Symbols.h"
 #include "lldb/Core/ModuleSpec.h"
+#include "lldb/Host/FileSystem.h"
 #include "lldb/Symbol/ObjectFile.h"
 #include "lldb/Target/Target.h"
 #include "lldb/Utility/ArchSpec.h"
 #include "lldb/Utility/DataBuffer.h"
 #include "lldb/Utility/DataExtractor.h"
 #include "lldb/Utility/Log.h"
 #include "lldb/Utility/SafeMachO.h"
 #include "lldb/Utility/StreamString.h"
if (symbol_file_spec.IsAbsolute() && symbol_file_spec.Exists())
     return symbol_file_spec;
 
   const char *symbol_filename = symbol_file_spec.GetFilename().AsCString();
   if (symbol_filename && symbol_filename[0]) {
     FileSpecList debug_file_search_paths(
         Target::GetDefaultDebugFileSearchPaths());
 
     // Add module directory.
-    const ConstString &file_dir = module_spec.GetFileSpec().GetDirectory();
+    FileSpec module_file_spec = module_spec.GetFileSpec();
+    // We keep the unresolved pathname if it fails.
+    FileSystem::ResolveSymbolicLink(module_file_spec, module_file_spec);
+
+    const ConstString &file_dir = module_file_spec.GetDirectory();
     debug_file_search_paths.AppendIfUnique(
         FileSpec(file_dir.AsCString("."), true));
 
     // Add current working directory.
     debug_file_search_paths.AppendIfUnique(FileSpec(".", true));
 
 #ifndef LLVM_ON_WIN32
 #if defined(__NetBSD__)
for (size_t idx = 0; idx < num_directories; ++idx) {
         files.push_back(dirname + file_dir.AsCString() + "/" + symbol_filename);
 
       const uint32_t num_files = files.size();
       for (size_t idx_file = 0; idx_file < num_files; ++idx_file) {
         const std::string &filename = files[idx_file];
         FileSpec file_spec(filename, true);
 
         if (llvm::sys::fs::equivalent(file_spec.GetPath(),
-                                      module_spec.GetFileSpec().GetPath()))
+                                      module_file_spec.GetPath()))
           continue;
 
         if (file_spec.Exists()) {
           lldb_private::ModuleSpecList specs;
           const size_t num_specs =
               ObjectFile::GetModuleSpecifications(file_spec, 0, 0, specs);
           assert(num_specs <= 1 &&
                  "Symbol Vendor supports only a single architecture");