Mordante updated this revision to Diff 236190.
Mordante added a comment.
Added support for some additional features:
- Allow limits from the C standard, either sharing the C++ constants or
separately.
- Allow to document the design choices for the limit.
- Allow to track the status of the limit. (This may become obsolete ones all
limits are implemented, but that can take a while.)
Added some additional fields to test the C support.
Removed the .inc file from the patch, this should not be committed.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D72053/new/
https://reviews.llvm.org/D72053
Files:
clang/docs/ImplementationQuantities.rst
clang/docs/UsersManual.rst
clang/include/clang/AST/Decl.h
clang/include/clang/AST/Type.h
clang/include/clang/Basic/CMakeLists.txt
clang/include/clang/Basic/ImplementationQuantities.h
clang/include/clang/Basic/ImplementationQuantities.td
clang/lib/CodeGen/CGRecordLayout.h
clang/lib/Frontend/CompilerInvocation.cpp
clang/utils/TableGen/CMakeLists.txt
clang/utils/TableGen/ClangImplementationQuantitiesEmitter.cpp
clang/utils/TableGen/TableGen.cpp
clang/utils/TableGen/TableGenBackends.h
Index: clang/utils/TableGen/TableGenBackends.h
===================================================================
--- clang/utils/TableGen/TableGenBackends.h
+++ clang/utils/TableGen/TableGenBackends.h
@@ -81,8 +81,14 @@
llvm::raw_ostream &OS);
void EmitClangCommentCommandList(llvm::RecordKeeper &Records,
llvm::raw_ostream &OS);
+
void EmitClangOpcodes(llvm::RecordKeeper &Records, llvm::raw_ostream &OS);
+void EmitClangImplementationQuantitiesDocs(llvm::RecordKeeper &Records,
+ llvm::raw_ostream &OS);
+void EmitClangImplementationQuantities(llvm::RecordKeeper &Records,
+ llvm::raw_ostream &OS);
+
void EmitNeon(llvm::RecordKeeper &Records, llvm::raw_ostream &OS);
void EmitFP16(llvm::RecordKeeper &Records, llvm::raw_ostream &OS);
void EmitNeonSema(llvm::RecordKeeper &Records, llvm::raw_ostream &OS);
Index: clang/utils/TableGen/TableGen.cpp
===================================================================
--- clang/utils/TableGen/TableGen.cpp
+++ clang/utils/TableGen/TableGen.cpp
@@ -60,6 +60,8 @@
GenClangCommentHTMLNamedCharacterReferences,
GenClangCommentCommandInfo,
GenClangCommentCommandList,
+ GenClangImplementationQuantitiesDocs,
+ GenClangImplementationQuantities,
GenClangOpenCLBuiltins,
GenArmNeon,
GenArmFP16,
@@ -172,6 +174,14 @@
clEnumValN(GenClangCommentCommandList, "gen-clang-comment-command-list",
"Generate list of commands that are used in "
"documentation comments"),
+ clEnumValN(GenClangImplementationQuantitiesDocs,
+ "gen-clang-implementation-quantities-docs",
+ "Generate documentation of the implementation quantities "
+ "as defined in the C++ standard"),
+ clEnumValN(GenClangImplementationQuantities,
+ "gen-clang-implementation-quantities",
+ "Generate of the implementation quantities "
+ "as defined in the C++ standard"),
clEnumValN(GenClangOpenCLBuiltins, "gen-clang-opencl-builtins",
"Generate OpenCL builtin declaration handlers"),
clEnumValN(GenArmNeon, "gen-arm-neon", "Generate arm_neon.h for clang"),
@@ -321,6 +331,12 @@
case GenClangCommentCommandList:
EmitClangCommentCommandList(Records, OS);
break;
+ case GenClangImplementationQuantitiesDocs:
+ EmitClangImplementationQuantitiesDocs(Records, OS);
+ break;
+ case GenClangImplementationQuantities:
+ EmitClangImplementationQuantities(Records, OS);
+ break;
case GenClangOpenCLBuiltins:
EmitClangOpenCLBuiltins(Records, OS);
break;
Index: clang/utils/TableGen/ClangImplementationQuantitiesEmitter.cpp
===================================================================
--- /dev/null
+++ clang/utils/TableGen/ClangImplementationQuantitiesEmitter.cpp
@@ -0,0 +1,131 @@
+//===--- ClangCommentCommandInfoEmitter.cpp - Generate command lists -----====//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/TableGen/Error.h"
+#include "llvm/TableGen/Record.h"
+#include "llvm/TableGen/StringMatcher.h"
+#include "llvm/TableGen/TableGenBackend.h"
+#include <vector>
+
+using namespace llvm;
+
+namespace clang {
+
+void EmitClangImplementationQuantitiesDocs(RecordKeeper &Records,
+ raw_ostream &OS) {
+ // Get the documentation introduction paragraph.
+ const Record *Documentation = Records.getDef("GlobalDocumentation");
+ if (!Documentation) {
+ llvm::PrintFatalError("The Documentation top-level definition is missing, "
+ "no documentation will be generated.");
+ return;
+ }
+
+ auto WriteValueAndSuffix = [&OS](Record *Tag) {
+ if (Tag->getValueAsBit("isBitLimit")) {
+ int Bits = Tag->getValueAsInt("Bits");
+ OS << ((1 << Bits) - 1) << " (" << Bits << " bits)";
+ } else if (Tag->getValueAsBit("isValueLimit"))
+ OS << Tag->getValueAsInt("Value") << '\n';
+ else if (Tag->getValueAsBit("isCompilerFlagLimit"))
+ OS << "Controlled by option '"
+ << Tag->getValueAsString("CompilerFlagOrDescription") << "' default "
+ << Tag->getValueAsInt("Value");
+ else if (Tag->getValueAsBit("isDescriptionLimit"))
+ OS << Tag->getValueAsString("CompilerFlagOrDescription");
+ else
+ OS << "*Unknown*";
+
+ std::string DC = Tag->getValueAsString("DesignChoices");
+ if (!DC.empty())
+ OS << "\n* Design choices: " << DC;
+
+ std::string Status = Tag->getValueAsString("Status");
+ if (!Status.empty())
+ OS << "\n* Status: " << Status;
+
+ OS << "\n\n";
+ };
+
+ OS << Documentation->getValueAsString("Intro");
+ std::vector<Record *> NonStandard;
+
+ OS << Documentation->getValueAsString("C");
+ for (auto Tag : Records.getAllDerivedDefinitions("IQ")) {
+ int Required = Tag->getValueAsInt("Required");
+ if (Required == 0) {
+ if (Tag->getValueAsInt("Recommended") == 0)
+ NonStandard.push_back(Tag);
+ continue;
+ }
+
+ std::string Decription = Tag->getValueAsString("Description_C_standard");
+ if (Decription.empty())
+ Decription = Tag->getValueAsString("Description");
+
+ OS << Decription << "\n* Required: " << Required << "\n* Clang: ";
+
+ WriteValueAndSuffix(Tag);
+ }
+
+ OS << Documentation->getValueAsString("CXX");
+ for (auto Tag : Records.getAllDerivedDefinitions("IQ")) {
+ int Recommended = Tag->getValueAsInt("Recommended");
+ if (Recommended == 0)
+ continue;
+
+ OS << Tag->getValueAsString("Description")
+ << "\n* Recommended: " << Recommended << "\n* Clang: ";
+
+ WriteValueAndSuffix(Tag);
+ }
+
+ if (NonStandard.empty())
+ return;
+
+ OS << Documentation->getValueAsString("Non_standard");
+
+ for (auto Tag : NonStandard) {
+ OS << Tag->getValueAsString("Description") << "\n* Clang: ";
+
+ WriteValueAndSuffix(Tag);
+ }
+}
+
+void EmitClangImplementationQuantities(RecordKeeper &Records, raw_ostream &OS) {
+ emitSourceFileHeader("A list of commands useable in documentation comments",
+ OS);
+
+ OS << "namespace IQ {\n";
+
+ for (auto Tag : Records.getAllDerivedDefinitions("IQ")) {
+ if (Tag->getValueAsBit("isDescriptionLimit"))
+ continue;
+
+ auto Name = Tag->getValueAsString("Name");
+ if (Name.empty())
+ continue;
+
+ if (Tag->getValueAsBit("isBitLimit")) {
+ int Bits = Tag->getValueAsInt("Bits");
+ OS << "constexpr unsigned " << Name << "Bits = " << Bits << ";\n";
+ OS << "constexpr unsigned Max" << Name << " = " << ((1u << Bits) - 1)
+ << ";\n";
+ } else if (Tag->getValueAsBit("isValueLimit"))
+ OS << "constexpr unsigned Max" << Name << " = "
+ << Tag->getValueAsInt("Value") << ";\n";
+ else if (Tag->getValueAsBit("isCompilerFlagLimit"))
+ OS << "constexpr unsigned " << Name
+ << "Default = " << Tag->getValueAsInt("Value") << ";\n";
+ else
+ PrintWarning("No tag set for \"" + Name + "\" no output is generated.");
+ }
+ OS << "} // IQ namespace\n\n";
+}
+
+} // end namespace clang
Index: clang/utils/TableGen/CMakeLists.txt
===================================================================
--- clang/utils/TableGen/CMakeLists.txt
+++ clang/utils/TableGen/CMakeLists.txt
@@ -11,6 +11,7 @@
ClangDataCollectorsEmitter.cpp
ClangDiagnosticsEmitter.cpp
ClangOpcodesEmitter.cpp
+ ClangImplementationQuantitiesEmitter.cpp
ClangOpenCLBuiltinEmitter.cpp
ClangOptionDocEmitter.cpp
ClangSACheckersEmitter.cpp
Index: clang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- clang/lib/Frontend/CompilerInvocation.cpp
+++ clang/lib/Frontend/CompilerInvocation.cpp
@@ -16,6 +16,7 @@
#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/DiagnosticOptions.h"
#include "clang/Basic/FileSystemOptions.h"
+#include "clang/Basic/ImplementationQuantities.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/LangStandard.h"
@@ -2847,8 +2848,8 @@
Opts.AccessControl = !Args.hasArg(OPT_fno_access_control);
Opts.ElideConstructors = !Args.hasArg(OPT_fno_elide_constructors);
Opts.MathErrno = !Opts.OpenCL && Args.hasArg(OPT_fmath_errno);
- Opts.InstantiationDepth =
- getLastArgIntValue(Args, OPT_ftemplate_depth, 1024, Diags);
+ Opts.InstantiationDepth = getLastArgIntValue(
+ Args, OPT_ftemplate_depth, IQ::InstantiationDepthDefault, Diags);
Opts.ArrowDepth =
getLastArgIntValue(Args, OPT_foperator_arrow_depth, 256, Diags);
Opts.ConstexprCallDepth =
Index: clang/lib/CodeGen/CGRecordLayout.h
===================================================================
--- clang/lib/CodeGen/CGRecordLayout.h
+++ clang/lib/CodeGen/CGRecordLayout.h
@@ -11,6 +11,7 @@
#include "clang/AST/CharUnits.h"
#include "clang/AST/DeclCXX.h"
+#include "clang/Basic/ImplementationQuantities.h"
#include "clang/Basic/LLVM.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/IR/DerivedTypes.h"
@@ -68,7 +69,7 @@
unsigned Offset : 16;
/// The total size of the bit-field, in bits.
- unsigned Size : 15;
+ unsigned Size : IQ::BitFieldBits;
/// Whether the bit-field is signed.
unsigned IsSigned : 1;
Index: clang/include/clang/Basic/ImplementationQuantities.td
===================================================================
--- /dev/null
+++ clang/include/clang/Basic/ImplementationQuantities.td
@@ -0,0 +1,196 @@
+//==--- ImplementationQuantities.td - Implementation quantities ----------===//
+//
+// 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
+//
+//===---------------------------------------------------------------------===//
+
+def GlobalDocumentation {
+ code Intro = [{..
+ -------------------------------------------------------------------
+ NOTE: This file is automatically generated by running clang-tblgen-gen
+ -clang-implementation-quantities-docs.Do not edit this file by hand !!
+ -------------------------------------------------------------------
+
+Introduction
+============
+
+This page lists the limits implemented in the Clang compiler. The available
+resources on the system running Clang may imposse other limits. For example,
+the system may have insufficient memory to compile the translation unit before
+the limits imposed by Clang are reached.
+
+}];
+
+ code C = [{
+C Standard defined quantities
+-----------------------------
+
+This is the list of limits as defined in the C standard's 'Translation limits'.
+
+}];
+
+ code CXX = [{
+C++ Standard defined quantities
+-------------------------------
+
+This contains the Implementation Quantities of Clang as required by Annex B of
+the C++ standard.
+
+}];
+
+code Non_standard = [{
+Non standard defined quantities
+-------------------------------
+
+These limits are defined in the standards, but are imposed in Clang.
+
+}];
+}
+
+class IQ<string N, string T, int R> {
+ // The variable base name
+ string Name = N;
+
+ // The description of the limit, often a copy from [implimits]
+ string Description = T;
+
+ // The description of the limit as documented in the C standard. If the value
+ // is the same as C++ leave it empty.
+ string Description_C_standard = "";
+
+ // If the limit is controlled by a compiler flag this field contains the name
+ // of the flag.
+ // If the limit is controlled by a description this field contains the
+ // description of the limit.
+ string CompilerFlagOrDescription = "";
+
+ // Explains the the design choices made in Clang. This should aid developers
+ // to determine why the current limit has been choosen so they can determine
+ // the impact of changing the value.
+ string DesignChoices = "";
+
+ // The status of the implementation and enforcing of the limit in Clang.
+ string Status = "";
+
+ // The recommended value of [implimits]. If the quantity is not a standard
+ // quantity it is set to 0.
+ int Recommended = R;
+
+ // The required number of Translation limits.
+ int Required = 0;
+
+ // The number of bits of the limit.
+ int Bits = 0;
+
+ // The numeric value of the limit.
+ int Value = 0;
+
+ // The type of limit used is determined by one of these bits:
+ // * isBitLimit The quantity is limited by a number of bits:
+ // * Bits Is the number of bits used
+ // * Value Contains maximum value based on the number of Bits as an unsigned
+ // bit-field.
+ // * isValueLimit The quantity is limited by a value:
+ // * Bits Unused.
+ // * Value The maximum value of the limit.
+ // * isCompilerFlagLimit The quantity is limited by a value based on a
+ // compiler flag:
+ // * Bits Unused.
+ // * Value The default value of the limit.
+ // * isDescriptionLimit The quantity's limit is described by a text. For
+ // exmple 'limited by the size of the stack'.
+ bit isBitLimit = 0;
+ bit isValueLimit = 0;
+ bit isCompilerFlagLimit = 0;
+ bit isDescriptionLimit = 0;
+}
+
+class IQImpl<string N, string T, int R, string DC, string S> : IQ<N, T, R> {
+ let DesignChoices = DC;
+ let Status = S;
+}
+
+class IQBits<string N, string T, int R, int B, string DC, string S>
+ : IQImpl<N, T, R, DC, S> {
+ let Bits = B;
+ let isBitLimit = 1;
+}
+
+class IQValue<string N, string T, int R, int V, string DC, string S>
+ : IQImpl<N, T, R, DC, S> {
+ let Value = V;
+ let isValueLimit = 1;
+}
+
+class IQCompilerFlag<string N, string T, int R, string CF, int V, string DC,
+ string S> : IQImpl<N, T, R, DC, S> {
+ let CompilerFlagOrDescription = CF;
+ let Value = V;
+ let isCompilerFlagLimit = 1;
+}
+
+class IQDescription<string N, string T, int R, string D, string DC, string S>
+ : IQImpl<N, T, R, DC, S> {
+ let CompilerFlagOrDescription = D;
+ let isDescriptionLimit = 1;
+}
+
+//
+// C only standard defined limits
+//
+
+let Required = 63 in
+def : IQ<"",
+ "Nesting levels of parenthesized declarators within a "
+ "full declarator", 0>;
+
+
+//
+// C/C++ Standard defined quantities
+//
+
+
+let Required = 63 in
+def : IQ<"", "Nesting levels of conditional inclusion.", 256>;
+
+
+let Required = 63,
+Description_C_standard = "Nesting levels of parenthesized declarators within "
+ "a full expression" in
+def : IQ<"",
+ "Nesting levels of parenthesized declarators within a "
+ "full-expression.", 256>;
+
+
+let Required = 127 in
+def : IQBits<"NumParams", "Parameters in one function definition.", 256, 16,
+ "Unknown", "At least partially implemented.">;
+
+def : IQCompilerFlag<"InstantiationDepth",
+ "Recursively nested template instantiations, including "
+ "substitution during template argumentdeduction.",
+ 1024, "-ftemplate-depth=N", 1024, "Unknown",
+ "At least partially implemented.">;
+
+//
+//
+// TODO copy the other quantities of the Standard's Annex B.
+//
+//
+
+
+//
+// Non standard defined quantities
+//
+
+def BitFieldWidth : IQBits<"BitField", "Maximum width of a bit-field.", 0, 15,
+ "This value avoids padding in "
+ "`CodeGen::CGBitFieldInfo::CGBitFieldInfo`.",
+ "Enforced by an assertion failure.">;
+
+def NestedFunctionPrototypes
+ : IQBits<"NumScopeDepthOrObjCQuals",
+ "Maximum number of nested function prototypes.", 0, 7,
+ "Unknown", "Unknown">;
Index: clang/include/clang/Basic/ImplementationQuantities.h
===================================================================
--- /dev/null
+++ clang/include/clang/Basic/ImplementationQuantities.h
@@ -0,0 +1,18 @@
+//===--- ImplementationQuantities.h ----------------------*- 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
+//
+//===--------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_BASIC_IMPLEMENTATIONQUANTITIES_H
+#define LLVM_CLANG_BASIC_IMPLEMENTATIONQUANTITIES_H
+
+namespace clang {
+
+#include "clang/Basic/ImplementationQuantities.inc"
+
+} // end namespace clang
+
+#endif
Index: clang/include/clang/Basic/CMakeLists.txt
===================================================================
--- clang/include/clang/Basic/CMakeLists.txt
+++ clang/include/clang/Basic/CMakeLists.txt
@@ -41,6 +41,12 @@
TARGET ClangAttrHasAttributeImpl
)
+clang_tablegen(ImplementationQuantities.inc -gen-clang-implementation-quantities
+ -I ${CMAKE_CURRENT_SOURCE_DIR}/../../
+ SOURCE ImplementationQuantities.td
+ TARGET ClangImplementationQuantities
+)
+
# ARM NEON and MVE
clang_tablegen(arm_neon.inc -gen-arm-neon-sema
SOURCE arm_neon.td
Index: clang/include/clang/AST/Type.h
===================================================================
--- clang/include/clang/AST/Type.h
+++ clang/include/clang/AST/Type.h
@@ -23,6 +23,7 @@
#include "clang/Basic/AttrKinds.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/ExceptionSpecificationType.h"
+#include "clang/Basic/ImplementationQuantities.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/Linkage.h"
#include "clang/Basic/PartialDiagnostic.h"
@@ -44,8 +45,8 @@
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/PointerLikeTypeTraits.h"
-#include "llvm/Support/type_traits.h"
#include "llvm/Support/TrailingObjects.h"
+#include "llvm/Support/type_traits.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
Index: clang/include/clang/AST/Decl.h
===================================================================
--- clang/include/clang/AST/Decl.h
+++ clang/include/clang/AST/Decl.h
@@ -25,6 +25,7 @@
#include "clang/Basic/AddressSpaces.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/IdentifierTable.h"
+#include "clang/Basic/ImplementationQuantities.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/Linkage.h"
#include "clang/Basic/OperatorKinds.h"
@@ -873,8 +874,6 @@
DAK_Normal
};
- enum { NumScopeDepthOrObjCQualsBits = 7 };
-
class ParmVarDeclBitfields {
friend class ASTDeclReader;
friend class ParmVarDecl;
@@ -901,7 +900,7 @@
/// Otherwise, the number of function parameter scopes enclosing
/// the function parameter scope in which this parameter was
/// declared.
- unsigned ScopeDepthOrObjCQuals : NumScopeDepthOrObjCQualsBits;
+ unsigned ScopeDepthOrObjCQuals : IQ::NumScopeDepthOrObjCQualsBits;
/// The number of parameters preceding this parameter in the
/// function parameter scope in which it was declared.
@@ -1627,7 +1626,7 @@
}
static constexpr unsigned getMaxFunctionScopeDepth() {
- return (1u << NumScopeDepthOrObjCQualsBits) - 1;
+ return IQ::MaxNumScopeDepthOrObjCQuals;
}
/// Returns the index of this parameter in its prototype or method scope.
Index: clang/docs/UsersManual.rst
===================================================================
--- clang/docs/UsersManual.rst
+++ clang/docs/UsersManual.rst
@@ -2389,7 +2389,8 @@
===================
The support for standard C in clang is feature-complete except for the
-C99 floating-point pragmas.
+C99 floating-point pragmas. For detailed information about implemented limits
+of C features please refer to :doc:`ImplementationQuantities`.
Extensions supported by clang
-----------------------------
@@ -2586,6 +2587,9 @@
Sets the limit for iterative calls to 'operator->' functions to N. The
default is 256.
+For detailed information about implemented limits of C++ features please
+refer to :doc:`ImplementationQuantities`.
+
.. _objc:
Objective-C Language Features
Index: clang/docs/ImplementationQuantities.rst
===================================================================
--- /dev/null
+++ clang/docs/ImplementationQuantities.rst
@@ -0,0 +1,81 @@
+..
+ -------------------------------------------------------------------
+ NOTE: This file is automatically generated by running clang-tblgen-gen
+ -clang-implementation-quantities-docs.Do not edit this file by hand !!
+ -------------------------------------------------------------------
+
+Introduction
+============
+
+This page lists the limits implemented in the Clang compiler. The available
+resources on the system running Clang may imposse other limits. For example,
+the system may have insufficient memory to compile the translation unit before
+the limits imposed by Clang are reached.
+
+
+C Standard defined quantities
+-----------------------------
+
+This is the list of limits as defined in the C standard's 'Translation limits'.
+
+Nesting levels of parenthesized declarators within a full declarator
+* Required: 63
+* Clang: *Unknown*
+
+Nesting levels of conditional inclusion.
+* Required: 63
+* Clang: *Unknown*
+
+Nesting levels of parenthesized declarators within a full expression
+* Required: 63
+* Clang: *Unknown*
+
+Parameters in one function definition.
+* Required: 127
+* Clang: 65535 (16 bits)
+* Design choices: Unknown
+* Status: At least partially implemented.
+
+
+C++ Standard defined quantities
+-------------------------------
+
+This contains the Implementation Quantities of Clang as required by Annex B of
+the C++ standard.
+
+Nesting levels of conditional inclusion.
+* Recommended: 256
+* Clang: *Unknown*
+
+Nesting levels of parenthesized declarators within a full-expression.
+* Recommended: 256
+* Clang: *Unknown*
+
+Parameters in one function definition.
+* Recommended: 256
+* Clang: 65535 (16 bits)
+* Design choices: Unknown
+* Status: At least partially implemented.
+
+Recursively nested template instantiations, including substitution during template argumentdeduction.
+* Recommended: 1024
+* Clang: Controlled by option '-ftemplate-depth=N' default 1024
+* Design choices: Unknown
+* Status: At least partially implemented.
+
+
+Non standard defined quantities
+-------------------------------
+
+These limits are defined in the standards, but are imposed in Clang.
+
+Maximum width of a bit-field.
+* Clang: 32767 (15 bits)
+* Design choices: This value avoids padding in `CodeGen::CGBitFieldInfo::CGBitFieldInfo`.
+* Status: Enforced by an assertion failure.
+
+Maximum number of nested function prototypes.
+* Clang: 127 (7 bits)
+* Design choices: Unknown
+* Status: Unknown
+
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