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Aug 7, 2025
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[Clang][NFC] Enumerate Clang ABI versions in a separate header file #151995

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8881837
Enumerate Clang abi versions in a separate header file
zwuis Aug 4, 2025
a5f6dcf
Add `ABI_VER_LATEST` macro
zwuis Aug 5, 2025
9dbaac6
Merge branch 'main' into clang-abi-ver
zwuis Aug 5, 2025
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127 changes: 127 additions & 0 deletions clang/include/clang/Basic/ABIVersions.def
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Original file line number Diff line number Diff line change
@@ -0,0 +1,127 @@
//===--- ABIVersions.def - Clang ABI Versions Database ----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file enumerates Clang ABI versions.
//
//===----------------------------------------------------------------------===//
//
/// @file ABIVersions.def
///
/// In this file, each of the Clang ABI Versions except "latest" is enumerated
/// ABI_VER_MAJOR_MINOR, or ABI_VER_MAJOR macro.
///
/// ABI_VER_MAJOR is used when the minor version is 0 or can be omitted.
///
/// The first argument of ABI_VER_MAJOR_MINOR and ABI_VER_MAJOR is the major
/// version.
///
/// The second argument of ABI_VER_MAJOR_MINOR is the minor version.

#if defined(ABI_VER_MAJOR_MINOR) != defined(ABI_VER_MAJOR)
# error ABI_VER_MAJOR_MINOR and ABI_VER_MAJOR should be defined simultaneously
#endif

#ifndef ABI_VER_MAJOR_MINOR
# define ABI_VER_MAJOR_MINOR(Major, Minor)
#endif

#ifndef ABI_VER_MAJOR
# define ABI_VER_MAJOR(Major)
#endif

/// Attempt to be ABI-compatible with code generated by Clang 3.8.x
/// (SVN r257626). This causes <1 x long long> to be passed in an integer
/// register instead of an SSE register on x64_64.
ABI_VER_MAJOR_MINOR(3, 8)

/// Attempt to be ABI-compatible with code generated by Clang 4.0.x
/// (SVN r291814). This causes move operations to be ignored when determining
/// whether a class type can be passed or returned directly.
ABI_VER_MAJOR(4)

/// Attempt to be ABI-compatible with code generated by Clang 6.0.x
/// (SVN r321711). This causes determination of whether a type is
/// standard-layout to ignore collisions between empty base classes and between
/// base classes and member subobjects, which affects whether we reuse base
/// class tail padding in some ABIs.
ABI_VER_MAJOR(6)

/// Attempt to be ABI-compatible with code generated by Clang 7.0.x
/// (SVN r338536). This causes alignof (C++) and _Alignof (C11) to be compatible
/// with __alignof (i.e., return the preferred alignment) rather than returning
/// the required alignment.
ABI_VER_MAJOR(7)

/// Attempt to be ABI-compatible with code generated by Clang 9.0.x
/// (SVN r351319). This causes vectors of __int128 to be passed in memory
/// instead of passing in multiple scalar registers on x86_64 on Linux and
/// NetBSD.
ABI_VER_MAJOR(9)

/// Attempt to be ABI-compatible with code generated by Clang 11.0.x
/// (git 2e10b7a39b93). This causes clang to pass unions with a 256-bit vector
/// member on the stack instead of using registers, to not properly mangle
/// substitutions for template names in some cases, and to mangle declaration
/// template arguments without a cast to the parameter type even when that can
/// lead to mangling collisions.
ABI_VER_MAJOR(11)

/// Attempt to be ABI-compatible with code generated by Clang 12.0.x
/// (git 8e464dd76bef). This causes clang to mangle lambdas within global-scope
/// inline variables incorrectly.
ABI_VER_MAJOR(12)

/// Attempt to be ABI-compatible with code generated by Clang 14.0.x.
/// This causes clang to:
/// - mangle dependent nested names incorrectly.
/// - make trivial only those defaulted copy constructors with a
/// parameter-type-list equivalent to the parameter-type-list of an implicit
/// declaration.
ABI_VER_MAJOR(14)

/// Attempt to be ABI-compatible with code generated by Clang 15.0.x.
/// This causes clang to:
/// - Reverse the implementation for CWG692, CWG1395 and CWG1432.
/// - pack non-POD members of packed structs.
/// - consider classes with defaulted special member functions non-pod.
ABI_VER_MAJOR(15)

/// Attempt to be ABI-compatible with code generated by Clang 17.0.x.
/// This causes clang to revert some fixes to its implementation of the Itanium
/// name mangling scheme, with the consequence that overloaded function
/// templates are mangled the same if they differ only by:
/// - constraints
/// - whether a non-type template parameter has a deduced type
/// - the parameter list of a template template parameter
ABI_VER_MAJOR(17)

/// Attempt to be ABI-compatible with code generated by Clang 18.0.x.
/// This causes clang to revert some fixes to the mangling of lambdas in the
/// initializers of members of local classes.
ABI_VER_MAJOR(18)

/// Attempt to be ABI-compatible with code generated by Clang 19.0.x.
/// This causes clang to:
/// - Incorrectly mangle the 'base type' substitutions of the CXX construction
/// vtable because it hasn't added 'type' as a substitution.
/// - Skip mangling enclosing class templates of member-like friend function
/// templates.
/// - Ignore empty struct arguments in C++ mode for ARM, instead of passing
/// them as if they had a size of 1 byte.
ABI_VER_MAJOR(19)

/// Attempt to be ABI-compatible with code generated by Clang 20.0.x.
/// This causes clang to:
/// - Incorrectly return C++ records in AVX registers on x86_64.
ABI_VER_MAJOR(20)

/// Conform to the underlying platform's C and C++ ABIs as closely as we can.
// (latest)

#undef ABI_VER_MAJOR_MINOR
#undef ABI_VER_MAJOR
92 changes: 4 additions & 88 deletions clang/include/clang/Basic/LangOptions.h
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Original file line number Diff line number Diff line change
Expand Up @@ -186,94 +186,10 @@ class LangOptionsBase {

/// Clang versions with different platform ABI conformance.
enum class ClangABI {
/// Attempt to be ABI-compatible with code generated by Clang 3.8.x
/// (SVN r257626). This causes <1 x long long> to be passed in an
/// integer register instead of an SSE register on x64_64.
Ver3_8,

/// Attempt to be ABI-compatible with code generated by Clang 4.0.x
/// (SVN r291814). This causes move operations to be ignored when
/// determining whether a class type can be passed or returned directly.
Ver4,

/// Attempt to be ABI-compatible with code generated by Clang 6.0.x
/// (SVN r321711). This causes determination of whether a type is
/// standard-layout to ignore collisions between empty base classes
/// and between base classes and member subobjects, which affects
/// whether we reuse base class tail padding in some ABIs.
Ver6,

/// Attempt to be ABI-compatible with code generated by Clang 7.0.x
/// (SVN r338536). This causes alignof (C++) and _Alignof (C11) to be
/// compatible with __alignof (i.e., return the preferred alignment)
/// rather than returning the required alignment.
Ver7,

/// Attempt to be ABI-compatible with code generated by Clang 9.0.x
/// (SVN r351319). This causes vectors of __int128 to be passed in memory
/// instead of passing in multiple scalar registers on x86_64 on Linux and
/// NetBSD.
Ver9,

/// Attempt to be ABI-compatible with code generated by Clang 11.0.x
/// (git 2e10b7a39b93). This causes clang to pass unions with a 256-bit
/// vector member on the stack instead of using registers, to not properly
/// mangle substitutions for template names in some cases, and to mangle
/// declaration template arguments without a cast to the parameter type
/// even when that can lead to mangling collisions.
Ver11,

/// Attempt to be ABI-compatible with code generated by Clang 12.0.x
/// (git 8e464dd76bef). This causes clang to mangle lambdas within
/// global-scope inline variables incorrectly.
Ver12,

/// Attempt to be ABI-compatible with code generated by Clang 14.0.x.
/// This causes clang to:
/// - mangle dependent nested names incorrectly.
/// - make trivial only those defaulted copy constructors with a
/// parameter-type-list equivalent to the parameter-type-list of an
/// implicit declaration.
Ver14,

/// Attempt to be ABI-compatible with code generated by Clang 15.0.x.
/// This causes clang to:
/// - Reverse the implementation for DR692, DR1395 and DR1432.
/// - pack non-POD members of packed structs.
/// - consider classes with defaulted special member functions non-pod.
Ver15,

/// Attempt to be ABI-compatible with code generated by Clang 17.0.x.
/// This causes clang to revert some fixes to its implementation of the
/// Itanium name mangling scheme, with the consequence that overloaded
/// function templates are mangled the same if they differ only by:
/// - constraints
/// - whether a non-type template parameter has a deduced type
/// - the parameter list of a template template parameter
Ver17,

/// Attempt to be ABI-compatible with code generated by Clang 18.0.x.
/// This causes clang to revert some fixes to the mangling of lambdas
/// in the initializers of members of local classes.
Ver18,

/// Attempt to be ABI-compatible with code generated by Clang 19.0.x.
/// This causes clang to:
/// - Incorrectly mangle the 'base type' substitutions of the CXX
/// construction vtable because it hasn't added 'type' as a substitution.
/// - Skip mangling enclosing class templates of member-like friend
/// function templates.
/// - Ignore empty struct arguments in C++ mode for ARM, instead of
/// passing them as if they had a size of 1 byte.
Ver19,

/// Attempt to be ABI-compatible with code generated by Clang 20.0.x.
/// This causes clang to:
/// - Incorrectly return C++ records in AVX registers on x86_64.
Ver20,

/// Conform to the underlying platform's C and C++ ABIs as closely
/// as we can.
#define ABI_VER_MAJOR_MINOR(Major, Minor) Ver##Major##_##Minor,
#define ABI_VER_MAJOR(Major) Ver##Major,
#include "clang/Basic/ABIVersions.def"

Latest
};

Expand Down
81 changes: 18 additions & 63 deletions clang/lib/Frontend/CompilerInvocation.cpp
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Expand Up @@ -3936,45 +3936,16 @@ void CompilerInvocationBase::GenerateLangArgs(const LangOptions &Opts,
GenerateArg(Consumer, OPT_fsanitize_ignorelist_EQ, F);

switch (Opts.getClangABICompat()) {
case LangOptions::ClangABI::Ver3_8:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "3.8");
#define ABI_VER_MAJOR_MINOR(Major, Minor) \
case LangOptions::ClangABI::Ver##Major##_##Minor: \
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, #Major "." #Minor); \
break;
case LangOptions::ClangABI::Ver4:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "4.0");
break;
case LangOptions::ClangABI::Ver6:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "6.0");
break;
case LangOptions::ClangABI::Ver7:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "7.0");
break;
case LangOptions::ClangABI::Ver9:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "9.0");
break;
case LangOptions::ClangABI::Ver11:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "11.0");
break;
case LangOptions::ClangABI::Ver12:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "12.0");
break;
case LangOptions::ClangABI::Ver14:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "14.0");
break;
case LangOptions::ClangABI::Ver15:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "15.0");
break;
case LangOptions::ClangABI::Ver17:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "17.0");
break;
case LangOptions::ClangABI::Ver18:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "18.0");
break;
case LangOptions::ClangABI::Ver19:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "19.0");
break;
case LangOptions::ClangABI::Ver20:
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, "20.0");
#define ABI_VER_MAJOR(Major) \
case LangOptions::ClangABI::Ver##Major: \
GenerateArg(Consumer, OPT_fclang_abi_compat_EQ, #Major ".0"); \
break;
#include "clang/Basic/ABIVersions.def"

case LangOptions::ClangABI::Latest:
break;
}
Expand Down Expand Up @@ -4482,32 +4453,16 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
!VerParts.second.getAsInteger(10, Minor)
: VerParts.first.size() == Ver.size() || VerParts.second == "0")) {
// Got a valid version number.
if (Major == 3 && Minor <= 8)
Opts.setClangABICompat(LangOptions::ClangABI::Ver3_8);
else if (Major <= 4)
Opts.setClangABICompat(LangOptions::ClangABI::Ver4);
else if (Major <= 6)
Opts.setClangABICompat(LangOptions::ClangABI::Ver6);
else if (Major <= 7)
Opts.setClangABICompat(LangOptions::ClangABI::Ver7);
else if (Major <= 9)
Opts.setClangABICompat(LangOptions::ClangABI::Ver9);
else if (Major <= 11)
Opts.setClangABICompat(LangOptions::ClangABI::Ver11);
else if (Major <= 12)
Opts.setClangABICompat(LangOptions::ClangABI::Ver12);
else if (Major <= 14)
Opts.setClangABICompat(LangOptions::ClangABI::Ver14);
else if (Major <= 15)
Opts.setClangABICompat(LangOptions::ClangABI::Ver15);
else if (Major <= 17)
Opts.setClangABICompat(LangOptions::ClangABI::Ver17);
else if (Major <= 18)
Opts.setClangABICompat(LangOptions::ClangABI::Ver18);
else if (Major <= 19)
Opts.setClangABICompat(LangOptions::ClangABI::Ver19);
else if (Major <= 20)
Opts.setClangABICompat(LangOptions::ClangABI::Ver20);
#define ABI_VER_MAJOR_MINOR(Major_, Minor_) \
if (std::tie(Major, Minor) <= std::tuple(Major_, Minor_)) \
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Suggested change
if (std::tie(Major, Minor) <= std::tuple(Major_, Minor_)) \
if (std::tie(Major, Minor) <= std::tie(Major_, Minor_)) \

?

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std::tie takes lvalue (function signature: std::tuple<Ts&...> std::tie(Ts&... args)), but arguments are integer literals (ABI_VER_MAJOR_MINOR(3, 8), see ABIVersions.def).

Opts.setClangABICompat(LangOptions::ClangABI::Ver##Major_##_##Minor_); \
else
#define ABI_VER_MAJOR(Major_) \
if (Major <= Major_) \
Opts.setClangABICompat(LangOptions::ClangABI::Ver##Major_); \
else
#include "clang/Basic/ABIVersions.def"
{} // sub-statement of the last else branch
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I wish we had some better way of writing this, but I've not come up with anything. :-)

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@JustinStitt JustinStitt Aug 4, 2025 •
edited
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The best I can think of is adding a ABI_VER_SENTINEL() to the end of the def file then we can lose the trailing {} with:

   if (Major <= Major_)                                                         \
     Opts.setClangABICompat(LangOptions::ClangABI::Ver##Major_);                \
   else
+#define ABI_VER_SENTINEL() 																										\
+      { /* Latest version - do nothing */ }
 #include "clang/Basic/ABIVersions.def"
-      {} // sub-statement of the last else branch
     } else if (Ver != "latest") {
       Diags.Report(diag::err_drv_invalid_value)
           << A->getAsString(Args) << A->getValue();

edit: your solution in a5f6dcf lgtm

} else if (Ver != "latest") {
Diags.Report(diag::err_drv_invalid_value)
<< A->getAsString(Args) << A->getValue();
Expand Down
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