[llvm][Dwarf] Add LanguageDescription API that accounts for version #162048

Michael137 · 2025-10-06T08:45:23Z

Currently llvm::dwarf::LanguageDescription returns a stringified DW_LNAME. It would be useful to have an API that returns the language name for a particular DW_LNAME_/version pair. LLDB's use case is that it wants to emit diagnostics with human readable descriptions of the language we got from debug-info (see #161688). We could maintain a side-table in LLDB but thought this might be generally useful and should live next to the existing LanguageDescription API.

llvmbot · 2025-10-06T08:45:59Z

@llvm/pr-subscribers-llvm-binary-utilities

@llvm/pr-subscribers-debuginfo

Author: Michael Buch (Michael137)

Changes

Currently llvm::dwarf::LanguageDescription returns a stringified DW_LNAME. It would be useful to have an API that returns the language name for a particular DW_LNAME_/version pair. LLDB's use case is that it wants to emit diagnostics with human readable descriptions of the language we got from debug-info. We could maintain a side-table in LLDB but thought this might be generally useful and should live next to the existing LanguageDescription API.

Full diff: https://github.com/llvm/llvm-project/pull/162048.diff

2 Files Affected:

(modified) llvm/include/llvm/BinaryFormat/Dwarf.h (+5)
(modified) llvm/lib/BinaryFormat/Dwarf.cpp (+111)

diff --git a/llvm/include/llvm/BinaryFormat/Dwarf.h b/llvm/include/llvm/BinaryFormat/Dwarf.h
index 2c5012510a5c3..de29f14097fb8 100644
--- a/llvm/include/llvm/BinaryFormat/Dwarf.h
+++ b/llvm/include/llvm/BinaryFormat/Dwarf.h
@@ -500,8 +500,13 @@ toDW_LNAME(SourceLanguage language) {
   return {};
 }
 
+/// Returns a version-independent language name.
 LLVM_ABI llvm::StringRef LanguageDescription(SourceLanguageName name);
 
+/// Returns a language name corresponding to the specified version.
+LLVM_ABI llvm::StringRef LanguageDescription(SourceLanguageName Name,
+                                             uint32_t Version);
+
 inline bool isCPlusPlus(SourceLanguage S) {
   bool result = false;
   // Deliberately enumerate all the language options so we get a warning when
diff --git a/llvm/lib/BinaryFormat/Dwarf.cpp b/llvm/lib/BinaryFormat/Dwarf.cpp
index 8b24044e19e50..8e87c68424e00 100644
--- a/llvm/lib/BinaryFormat/Dwarf.cpp
+++ b/llvm/lib/BinaryFormat/Dwarf.cpp
@@ -472,6 +472,117 @@ StringRef llvm::dwarf::LanguageDescription(dwarf::SourceLanguageName lname) {
   return "Unknown";
 }
 
+StringRef llvm::dwarf::LanguageDescription(dwarf::SourceLanguageName Name,
+                                           uint32_t Version) {
+  switch (Name) {
+  // YYYY
+  case DW_LNAME_Ada: {
+    if (Version <= 1983)
+      return "Ada 83";
+    if (Version <= 1995)
+      return "Ada 95";
+    if (Version <= 2005)
+      return "Ada 2005";
+    if (Version <= 2012)
+      return "Ada 2012";
+  } break;
+
+  case DW_LNAME_Cobol: {
+    if (Version <= 1974)
+      return "COBOL-74";
+    if (Version <= 1985)
+      return "COBOL-85";
+  } break;
+
+  case DW_LNAME_Fortran: {
+    if (Version <= 1977)
+      return "FORTRAN 77";
+    if (Version <= 1990)
+      return "FORTRAN 90";
+    if (Version <= 1995)
+      return "Fortran 95";
+    if (Version <= 2003)
+      return "Fortran 2003";
+    if (Version <= 2008)
+      return "Fortran 2008";
+    if (Version <= 2018)
+      return "Fortran 2018";
+  } break;
+
+  // YYYYMM
+  case DW_LNAME_C: {
+    if (Version == 0)
+      return "K&R C";
+    if (Version <= 198912)
+      return "C89";
+    if (Version <= 199901)
+      return "C99";
+    if (Version <= 201112)
+      return "C11";
+    if (Version <= 201710)
+      return "C17";
+  } break;
+
+  case DW_LNAME_C_plus_plus: {
+    if (Version == 0)
+      break;
+    if (Version <= 199711)
+      return "C++98";
+    if (Version <= 200310)
+      return "C++03";
+    if (Version <= 201103)
+      return "C++11";
+    if (Version <= 201402)
+      return "C++14";
+    if (Version <= 201703)
+      return "C++17";
+    if (Version <= 202002)
+      return "C++20";
+  } break;
+
+  case DW_LNAME_ObjC_plus_plus:
+  case DW_LNAME_ObjC:
+  case DW_LNAME_Move:
+  case DW_LNAME_SYCL:
+  case DW_LNAME_BLISS:
+  case DW_LNAME_Crystal:
+  case DW_LNAME_D:
+  case DW_LNAME_Dylan:
+  case DW_LNAME_Go:
+  case DW_LNAME_Haskell:
+  case DW_LNAME_HLSL:
+  case DW_LNAME_Java:
+  case DW_LNAME_Julia:
+  case DW_LNAME_Kotlin:
+  case DW_LNAME_Modula2:
+  case DW_LNAME_Modula3:
+  case DW_LNAME_OCaml:
+  case DW_LNAME_OpenCL_C:
+  case DW_LNAME_Pascal:
+  case DW_LNAME_PLI:
+  case DW_LNAME_Python:
+  case DW_LNAME_RenderScript:
+  case DW_LNAME_Rust:
+  case DW_LNAME_Swift:
+  case DW_LNAME_UPC:
+  case DW_LNAME_Zig:
+  case DW_LNAME_Assembly:
+  case DW_LNAME_C_sharp:
+  case DW_LNAME_Mojo:
+  case DW_LNAME_GLSL:
+  case DW_LNAME_GLSL_ES:
+  case DW_LNAME_OpenCL_CPP:
+  case DW_LNAME_CPP_for_OpenCL:
+  case DW_LNAME_Ruby:
+  case DW_LNAME_Hylo:
+  case DW_LNAME_Metal:
+    break;
+  }
+
+  // Fallback to un-versioned name.
+  return LanguageDescription(Name);
+}
+
 StringRef llvm::dwarf::CaseString(unsigned Case) {
   switch (Case) {
   case DW_ID_case_sensitive:

dwblaikie

Be good to have some test coverage - either as a unit test, or if there's some useful way to render this data in llvm-dwarfdump, even better.

dwblaikie · 2025-10-06T16:26:41Z

llvm/lib/BinaryFormat/Dwarf.cpp

+    if (Version <= 1983)
+      return "Ada 83";
+    if (Version <= 1995)
+      return "Ada 95";
+    if (Version <= 2005)
+      return "Ada 2005";
+    if (Version <= 2012)
+      return "Ada 2012";


I'd have expected these to work the other way around - like if the Version is < 1995, then it's Ada 83.

Might be weird to say it's Ada95 when the version is 1990/before 1995? But I'm not sure if there's a clear general sense, or language-specific sense, of what the intermediate values should mean.

Yea those intermediate values haven't really been specified i think. I took inspiration from the logic in:

llvm-project/llvm/include/llvm/BinaryFormat/Dwarf.h

Lines 228 to 273 in c2765b7

/// Convert a DWARF 6 pair of language name and version to a DWARF 5 DW_LANG.

/// If the version number doesn't exactly match a known version it is

/// rounded up to the next-highest known version number.

inline std::optional<SourceLanguage> toDW_LANG(SourceLanguageName name,

uint32_t version) {

switch (name) {

case DW_LNAME_Ada: // YYYY

if (version <= 1983)

return DW_LANG_Ada83;

if (version <= 1995)

return DW_LANG_Ada95;

if (version <= 2005)

return DW_LANG_Ada2005;

if (version <= 2012)

return DW_LANG_Ada2012;

return {};

case DW_LNAME_BLISS:

return DW_LANG_BLISS;

case DW_LNAME_C: // YYYYMM, K&R 000000

if (version == 0)

return DW_LANG_C;

if (version <= 198912)

return DW_LANG_C89;

if (version <= 199901)

return DW_LANG_C99;

if (version <= 201112)

return DW_LANG_C11;

if (version <= 201710)

return DW_LANG_C17;

return {};

case DW_LNAME_C_plus_plus: // YYYYMM

if (version == 0)

return DW_LANG_C_plus_plus;

if (version <= 199711)

return DW_LANG_C_plus_plus;

if (version <= 200310)

return DW_LANG_C_plus_plus_03;

if (version <= 201103)

return DW_LANG_C_plus_plus_11;

if (version <= 201402)

return DW_LANG_C_plus_plus_14;

if (version <= 201703)

return DW_LANG_C_plus_plus_17;

if (version <= 202002)

return DW_LANG_C_plus_plus_20;

return {};

There we round up the intermediate version number. Reading https://dwarfstd.org/languages-v6.html, it sounds like the version number specifies the completion of a particular language version. Anything after that is the next version. At least that's how I think about this

Seems like a reasonable way to deal with pre-release compilers that guess the final date of the standard incorrectly. The other alternative would be put the raw version in the string.

Michael137 · 2025-10-06T20:28:02Z

Be good to have some test coverage - either as a unit test, or if there's some useful way to render this data in llvm-dwarfdump, even better.

Added unittests in latest commit. Testing using dwarfdump wouldn't work yet because we don't emit version names yet in LLVM (LLDB synthesizes them from the DW_LANG_ codes). Once we implement the DWARFv6 language version scheme (which I'm currently doing but don't have anything to review yet), we could test this further.

adrian-prantl

I don't have super strong opinions about the rounding, but it seems reasonable to me.

dwblaikie · 2025-10-06T21:22:50Z

llvm/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp

  });
 }

+TEST(DWARFDebugInfo, TestLanguageDescription_Versioned) {


there's probably some kind of table-based testing approach that might be tidier?

Hmmm agreed it would be nice to add some more coverage. Not sure off the top how we'd do this with a table though, without duplicating the language strings (which would kind of defeat the purpose of the test).

Not sure I follow.

What I was picturing was a gunit TEST_P (see, for example, DumpValueFixture in llvm/unittests/DebugInfo/DWARF/DWARFFormValueTest.cpp)

Oh I see what you mean. Yea we can make it a parameterized test for sure

Will do in a follow-up!

Currently `llvm::dwarf::LanguageDescription` returns a stringified `DW_LNAME`. It would be useful to have an API that returns the language name for a particular `DW_LNAME_`/version pair. LLDB's use case is that it wants to display a human readable description of the language we got from debug-info in diagnostics. We could maintain a side-table in LLDB but though this might generally be useful to live next to the `LanguageDescription` API.

…sion (#162050) Depends on #162048 This makes sure we also include the version number in the description. For `C++17`, this would, e.g., now return `"C++17"` instead of `"ISO C++"`.

…anguage version (#162050) Depends on llvm/llvm-project#162048 This makes sure we also include the version number in the description. For `C++17`, this would, e.g., now return `"C++17"` instead of `"ISO C++"`.

Michael137 requested review from adrian-prantl and dwblaikie October 6, 2025 08:45

llvmbot added debuginfo llvm:binary-utilities labels Oct 6, 2025

This was referenced Oct 6, 2025

[lldb][Expression] Emit a 'Note' diagnostic that indicates the language used for expression evaluation #161688

Open

[lldb][Language] Make SourceLanguage::GetDescription for language version #162050

Merged

dwblaikie reviewed Oct 6, 2025

View reviewed changes

adrian-prantl approved these changes Oct 7, 2025

View reviewed changes

dwblaikie approved these changes Oct 7, 2025

View reviewed changes

Michael137 added 5 commits October 8, 2025 17:54

fixup! expand docs

335d824

fixup! handle C version 0

427784d

fixup! unittests

1c62bcc

fixup! move tests, remove redundant casts

924d111

Michael137 force-pushed the llvm/dwarf-versioned-language-name branch from f322710 to 924d111 Compare October 8, 2025 16:55

fixup! add back newline

70e3ed1

Michael137 enabled auto-merge (squash) October 8, 2025 17:26

Michael137 merged commit 030d8e6 into llvm:main Oct 8, 2025
7 of 8 checks passed

Michael137 deleted the llvm/dwarf-versioned-language-name branch October 8, 2025 17:34

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[llvm][Dwarf] Add LanguageDescription API that accounts for version #162048

[llvm][Dwarf] Add LanguageDescription API that accounts for version #162048

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	/// Convert a DWARF 6 pair of language name and version to a DWARF 5 DW_LANG.
	/// If the version number doesn't exactly match a known version it is
	/// rounded up to the next-highest known version number.
	inline std::optional<SourceLanguage> toDW_LANG(SourceLanguageName name,
	uint32_t version) {
	switch (name) {
	case DW_LNAME_Ada: // YYYY
	if (version <= 1983)
	return DW_LANG_Ada83;
	if (version <= 1995)
	return DW_LANG_Ada95;
	if (version <= 2005)
	return DW_LANG_Ada2005;
	if (version <= 2012)
	return DW_LANG_Ada2012;
	return {};
	case DW_LNAME_BLISS:
	return DW_LANG_BLISS;
	case DW_LNAME_C: // YYYYMM, K&R 000000
	if (version == 0)
	return DW_LANG_C;
	if (version <= 198912)
	return DW_LANG_C89;
	if (version <= 199901)
	return DW_LANG_C99;
	if (version <= 201112)
	return DW_LANG_C11;
	if (version <= 201710)
	return DW_LANG_C17;
	return {};
	case DW_LNAME_C_plus_plus: // YYYYMM
	if (version == 0)
	return DW_LANG_C_plus_plus;
	if (version <= 199711)
	return DW_LANG_C_plus_plus;
	if (version <= 200310)
	return DW_LANG_C_plus_plus_03;
	if (version <= 201103)
	return DW_LANG_C_plus_plus_11;
	if (version <= 201402)
	return DW_LANG_C_plus_plus_14;
	if (version <= 201703)
	return DW_LANG_C_plus_plus_17;
	if (version <= 202002)
	return DW_LANG_C_plus_plus_20;
	return {};

[llvm][Dwarf] Add LanguageDescription API that accounts for version #162048

[llvm][Dwarf] Add LanguageDescription API that accounts for version #162048

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