capnproto

source-location.h (4830B)

---

 // Copyright (c) 2021 Cloudflare, Inc. and contributors
 // Licensed under the MIT License:
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
 // in the Software without restriction, including without limitation the rights
 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 // copies of the Software, and to permit persons to whom the Software is
 // furnished to do so, subject to the following conditions:
 //
 // The above copyright notice and this permission notice shall be included in
 // all copies or substantial portions of the Software.
 //
 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
 #pragma once
 
 #include "string.h"
 
 // GCC does not implement __builtin_COLUMN() as that's non-standard but MSVC & clang do.
 // MSVC does as of version https://github.com/microsoft/STL/issues/54) but there's currently not any
 // pressing need for this for MSVC & writing the write compiler version check is annoying.
 // Checking for clang version is problematic due to the way that XCode lies about __clang_major__.
 // Instead we use __has_builtin as the feature check to check clang.
 // Context: https://github.com/capnproto/capnproto/issues/1305
 #ifdef __has_builtin
 #if __has_builtin(__builtin_COLUMN)
 #define KJ_CALLER_COLUMN() __builtin_COLUMN()
 #else
 #define KJ_CALLER_COLUMN() 0
 #endif
 #else
 #define KJ_CALLER_COLUMN() 0
 #endif
 
 #if __cplusplus > 201703L
 #define KJ_COMPILER_SUPPORTS_SOURCE_LOCATION 1
 #elif defined(__has_builtin)
 // Clang 9 added these builtins: https://releases.llvm.org/9.0.0/tools/clang/docs/LanguageExtensions.html
 // Use __has_builtin as the way to detect this because __clang_major__ is unreliable (see above
 // about issue with Xcode-provided clang).
 #define KJ_COMPILER_SUPPORTS_SOURCE_LOCATION (   \
   __has_builtin(__builtin_FILE) &&               \
   __has_builtin(__builtin_LINE) &&               \
   __has_builtin(__builtin_FUNCTION)              \
   )
 #elif __GNUC__ >= 5
 // GCC 5 supports the required builtins: https://gcc.gnu.org/onlinedocs/gcc-5.1.0/gcc/Other-Builtins.html
 #define KJ_COMPILER_SUPPORTS_SOURCE_LOCATION 1
 #endif
 
 namespace kj {
 class SourceLocation {
   // libc++ doesn't seem to implement <source_location> (or even <experimental/source_location>), so
   // this is a non-STL wrapper over the compiler primitives (these are the same across MSVC/clang/
   // gcc). Additionally this uses kj::StringPtr for holding the strings instead of const char* which
   // makes it integrate a little more nicely into KJ.
 
   struct Badge { explicit constexpr Badge() = default; };
   // Neat little trick to make sure we can never call SourceLocation with explicit arguments.
 public:
 #if !KJ_COMPILER_SUPPORTS_SOURCE_LOCATION
   constexpr SourceLocation() : fileName("??"), function("??"), lineNumber(0), columnNumber(0) {}
   // Constructs a dummy source location that's not pointing at anything.
 #else
   constexpr SourceLocation(Badge = Badge{}, const char* file = __builtin_FILE(),
       const char* func = __builtin_FUNCTION(), uint line = __builtin_LINE(),
       uint column = KJ_CALLER_COLUMN())
     : fileName(file), function(func), lineNumber(line), columnNumber(column)
   {}
 #endif
 
 #if KJ_COMPILER_SUPPORTS_SOURCE_LOCATION
   // This can only be exposed if we actually generate valid SourceLocation objects as otherwise all
   // SourceLocation objects would confusingly (and likely problematically) be equated equal.
   constexpr bool operator==(const SourceLocation& o) const {
     // Pointer equality is fine here based on how SourceLocation operates & how compilers will
     // intern all duplicate string constants.
     return fileName == o.fileName && function == o.function && lineNumber == o.lineNumber &&
         columnNumber == o.columnNumber;
   }
 #endif
 
   const char* fileName;
   const char* function;
   uint lineNumber;
   uint columnNumber;
 };
 
 kj::String KJ_STRINGIFY(const SourceLocation& l);
 
 class NoopSourceLocation {
   // This is used in places where we want to conditionally compile out tracking the source location.
   // As such it intentionally lacks all the features but the default constructor so that the API
   // isn't accidentally used in the wrong compilation context.
 };
 
 KJ_UNUSED static kj::String KJ_STRINGIFY(const NoopSourceLocation& l) {
   return kj::String();
 }
 }  // namespace kj