-
Notifications
You must be signed in to change notification settings - Fork 14.3k
[LLDB] Warn about truncated DWARF section names on Windows #145175
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.
Already on GitHub? Sign in to your account
base: main
Are you sure you want to change the base?
Conversation
@llvm/pr-subscribers-lldb Author: nerix (Nerixyz) ChangesLinking executables with DWARF sections on Windows with the default link.exe will truncate the section names, as sections in PE/COFF executable images can't be longer than 8 bytes. There's no warning about this. When trying to debug these executables in LLDB, no debug info will be loaded, because LLDB won't find the required sections and it doesn't find CodeView debug info. There's no warning here, either (this PR adds one). I ran into this myself while playing around with LLDB:
The fix would be to pass This PR adds a warning when LLDB detects truncated DWARF sections (i.e. sections matching
I included the additional note, because to get to this point, one would have to have used Clang on windows-msvc (on MinGW, the default linker doesn't truncate the names), so they should have lld-link available as well. Full diff: https://github.com/llvm/llvm-project/pull/145175.diff 4 Files Affected:
diff --git a/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp b/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
index 4984445dcbab9..343d7477c66c7 100644
--- a/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
+++ b/lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp
@@ -1036,12 +1036,19 @@ void ObjectFilePECOFF::CreateSections(SectionList &unified_section_list) {
m_sections_up->AddSection(header_sp);
unified_section_list.AddSection(header_sp);
+ std::vector<llvm::StringRef> truncated_dwarf_sections;
const uint32_t nsects = m_sect_headers.size();
for (uint32_t idx = 0; idx < nsects; ++idx) {
llvm::StringRef sect_name = GetSectionName(m_sect_headers[idx]);
ConstString const_sect_name(sect_name);
SectionType section_type = GetSectionType(sect_name, m_sect_headers[idx]);
+ // Detect unknown sections matching ^\.debug_[a-z]$
+ if (section_type == eSectionTypeOther && sect_name.size() == 8 &&
+ sect_name.starts_with(".debug_") && llvm::isLower(sect_name.back())) {
+ truncated_dwarf_sections.emplace_back(sect_name);
+ }
+
SectionSP section_sp(new Section(
module_sp, // Module to which this section belongs
this, // Object file to which this section belongs
@@ -1071,6 +1078,16 @@ void ObjectFilePECOFF::CreateSections(SectionList &unified_section_list) {
m_sections_up->AddSection(section_sp);
unified_section_list.AddSection(section_sp);
}
+
+ if (!truncated_dwarf_sections.empty()) {
+ module_sp->ReportWarning(
+ "contains {} truncated DWARF sections ({}).\n"
+ "Note: Executable images on Windows can't include the required names "
+ "when linking with the default link.exe. A third party linker like "
+ "lld-link is required (compile with -fuse-ld=lld-link on Clang).",
+ truncated_dwarf_sections.size(),
+ llvm::join(truncated_dwarf_sections, ", "));
+ }
}
}
diff --git a/lldb/test/Shell/ObjectFile/PECOFF/lit.local.cfg b/lldb/test/Shell/ObjectFile/PECOFF/lit.local.cfg
index 9ef350be1dee2..1ae00d07fc3e6 100644
--- a/lldb/test/Shell/ObjectFile/PECOFF/lit.local.cfg
+++ b/lldb/test/Shell/ObjectFile/PECOFF/lit.local.cfg
@@ -1 +1 @@
-config.suffixes = ['.yaml', '.test']
+config.suffixes = ['.yaml', '.test', '.c']
diff --git a/lldb/test/Shell/ObjectFile/PECOFF/truncated-dwarf.c b/lldb/test/Shell/ObjectFile/PECOFF/truncated-dwarf.c
new file mode 100644
index 0000000000000..92cb61050142a
--- /dev/null
+++ b/lldb/test/Shell/ObjectFile/PECOFF/truncated-dwarf.c
@@ -0,0 +1,7 @@
+// REQUIRES: target-windows
+// RUN: %build --compiler=clang-cl --force-dwarf-symbols --force-ms-link -o %t.exe -- %s
+// RUN: %lldb -f %t.exe 2>&1 | FileCheck %s
+
+int main(void) {}
+
+// CHECK: warning: {{.*}} contains 4 truncated DWARF sections (.debug_{{[a-z]}}, .debug_{{[a-z]}}, .debug_{{[a-z]}}, .debug_{{[a-z]}})
diff --git a/lldb/test/Shell/helper/build.py b/lldb/test/Shell/helper/build.py
index caaa14f90af1c..ecb02c1d7c87f 100755
--- a/lldb/test/Shell/helper/build.py
+++ b/lldb/test/Shell/helper/build.py
@@ -173,6 +173,22 @@
help="Specify the C/C++ standard.",
)
+if sys.platform == "win32":
+ parser.add_argument(
+ "--force-dwarf-symbols",
+ dest="force_dwarf_symbols",
+ action="store_true",
+ default=False,
+ help="When compiling with clang-cl on Windows, use DWARF instead of CodeView",
+ )
+ parser.add_argument(
+ "--force-ms-link",
+ dest="force_ms_link",
+ action="store_true",
+ default=False,
+ help="When compiling with clang-cl on Windows, always use link.exe",
+ )
+
args = parser.parse_args(args=sys.argv[1:])
@@ -379,15 +395,20 @@ def __init__(self, toolchain_type, args):
)
if self.mode == "link" or self.mode == "compile-and-link":
- self.linker = (
- self._find_linker("link")
- if toolchain_type == "msvc"
- else self._find_linker("lld-link", args.tools_dir)
- )
+ if toolchain_type == "msvc" or args.force_ms_link:
+ search_paths = []
+ if toolchain_type != "msvc":
+ search_paths.append(
+ os.path.dirname(find_executable("cl", args.tools_dir))
+ )
+ self.linker = self._find_linker("link", search_paths)
+ else:
+ self.linker = self._find_linker("lld-link", args.tools_dir)
if not self.linker:
raise ValueError("Unable to find an appropriate linker.")
self.compile_env, self.link_env = self._get_visual_studio_environment()
+ self.force_dwarf_symbols = args.force_dwarf_symbols
def _find_linker(self, name, search_paths=[]):
compiler_dir = os.path.dirname(self.compiler)
@@ -678,6 +699,8 @@ def _get_compilation_command(self, source, obj):
args.append("/GR-")
args.append("/Z7")
if self.toolchain_type == "clang-cl":
+ if self.force_dwarf_symbols:
+ args.append("-gdwarf")
args.append("-Xclang")
args.append("-fkeep-static-consts")
args.append("-fms-compatibility-version=19")
|
b58c2be
to
d2e8656
Compare
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
Looks reasonable to me.
d2e8656
to
c4ded34
Compare
Linking executables with DWARF sections on Windows with the default link.exe will truncate the section names, as sections in PE/COFF executable images can't be longer than 8 bytes. There's no warning about this. When trying to debug these executables in LLDB, no debug info will be loaded, because LLDB won't find the required sections and it doesn't find CodeView debug info. There's no warning here, either (this PR adds one).
I ran into this myself while playing around with LLDB:
clang-cl foo.c -gdwarf -o foo.exe
lldb foo.exe
b foo.c:10
⚡ → "Unable to resolve breakpoint to any actual locations." (because no debug info is loaded)The fix would be to pass
-fuse-ld=lld-link
to Clang.This PR adds a warning when LLDB detects truncated DWARF sections (i.e. sections matching
^\.debug_[a-z]$
):I included the additional note, because to get to this point, one would have to have used Clang on windows-msvc (on MinGW, the default linker doesn't truncate the names), so they should have lld-link available as well.