Add cppdemangle in druntime

Having a C++ symbol demangler is very useful, with this it will
be possible to implement the C++ symbol demangle in the stacktrace.

The demangling is done in Posix platform by function __cxa_demangle
presents in Itanium C++ ABI (https://itanium-cxx-abi.github.io/cxx-abi/abi.html#demangler).

Itanium C++ ABI is used practically in all modern C++ compilers on Posix,
however old compilers (like GCC < 3.0) used a different name mangling,
this is not a problem because DMD in fact only supports Itanium C++ ABI on Posix.

For Windows instead the implementation it is provided by the UnDecorateSymbolName
function present in the Debug Help Library.
(https://docs.microsoft.com/en-us/windows/win32/api/dbghelp/nf-dbghelp-undecoratesymbolname)

Signed-off-by: Ernesto Castellotti <mail@ernestocastellotti.it>

mak/COPY

@@ -25,6 +25,7 @@ COPY=\
 	$(IMPDIR)\core\internal\atomic.d \
 	$(IMPDIR)\core\internal\attributes.d \
 	$(IMPDIR)\core\internal\convert.d \
+	$(IMPDIR)\core\internal\cppdemangle.d \
 	$(IMPDIR)\core\internal\dassert.d \
 	$(IMPDIR)\core\internal\destruction.d \
 	$(IMPDIR)\core\internal\entrypoint.d \

mak/SRCS

@@ -25,6 +25,7 @@ SRCS=\
 	src\core\internal\atomic.d \
 	src\core\internal\attributes.d \
 	src\core\internal\convert.d \
+	src\core\internal\cppdemangle.d \
 	src\core\internal\dassert.d \
 	src\core\internal\destruction.d \
 	src\core\internal\entrypoint.d \

mak/WINDOWS

@@ -132,6 +132,9 @@ $(IMPDIR)\core\internal\attributes.d : src\core\internal\attributes.d
 $(IMPDIR)\core\internal\convert.d : src\core\internal\convert.d
 	copy $** $@
 
+$(IMPDIR)\core\internal\cppdemangle.d : src\core\internal\cppdemangle.d
+	copy $** $@
+
 $(IMPDIR)\core\internal\dassert.d : src\core\internal\dassert.d
 	copy $** $@
 

src/core/internal/cppdemangle.d

@@ -0,0 +1,311 @@
+/**
+* This module provides functions to demangle C++ symbols
+*
+* For POSIX platforms the function `__cxa_demangle` present in Itanium C++ ABI does the demangling, therefore this module
+* depends on the C++ standard library which must be linked dynamically or available for research through the dynamic loader.
+*
+* For Windows platform the function `UnDecorateSymbolName` present in the Debug Help Library does the demangling,
+* which should be available for all versions of Windows supported by D.
+*
+* Copyright: Copyright © 2020, The D Language Foundation
+* License: $(HTTP www.boost.org/LICENSE_1_0.txt, Boost License 1.0).
+* Authors: Ernesto Castellotti
+* Source: $(DRUNTIMESRC core/internal/_cppdemangle.d)
+* See_Also:
+*      https://itanium-cxx-abi.github.io/cxx-abi/abi.html#demangler
+*      https://gcc.gnu.org/onlinedocs/libstdc++/libstdc++-html-USERS-4.3/a01696.html
+*      https://libcxxabi.llvm.org/spec.html
+*      https://docs.microsoft.com/en-us/windows/win32/api/dbghelp/nf-dbghelp-undecoratesymbolname
+*/
+module core.internal.cppdemangle;
+
+/**
+* Demangles C++ mangled names.
+*
+* The output buffer and return will be contains the demangled name of C++ symbol if the demangling is successful.
+*
+* This function will fail and the mangled name in input will be returned if:
+* 1. The symbol to be processed does not follow the Itanium ABI for POSIX or Visual C++ for Windows, or more simply it is not a C++ name
+* 2. The platform is not compatible or the library needed to perform the demangling was not found or linked with the executable
+* 3. The size of the output buffer is not sufficient to contain the demangled name with its prefix
+*
+* This function will fail and null will be returned if:
+* 1. The output buffer is null
+* 2. The function has failed (see list above) and output buffer is unable to contain the mangled name in input
+*
+ * Params:
+ *  mangledName = The string to demangle.
+ *  outputBuffer = The destination buffer, if the size of the destination buffer is <= the size of cppdemangle output the return string would be incomplete.
+ *  prefix = Specifies the prefix to be added to the beginning of the string containing the demangled name
+ *
+ * Returns:
+ *  The demangled name or the original string if the name is not a mangled C++ name.
+ */
+char[] cppdemangle(const(char)[] mangledName, char[] outputBuffer, string prefix = "") @trusted
+{
+    CPPDemangle.initialize();
+    return CPPDemangle.instance.cppdemangle(mangledName, outputBuffer, prefix);
+}
+
+package struct CPPDemangle
+{
+    private __gshared CPPDemangle _instance;
+    private __gshared bool isInitialized;
+
+    version (Posix)
+    {
+        @nogc nothrow extern(C)
+        {
+            private extern(C) char* function(const char* mangledName, char* outputBuffer, size_t* length, int* status) __cxa_demangle;
+        }
+
+        version (OSX)
+            private static immutable names = ["libc++abi.dylib", "libstdc++.dylib"];
+        else
+        {
+            private static immutable names = ["libstdc++.so", "libstdc++.so.6", "libstdc++.so.5",
+                "libc++abi.so", "libc++abi.so.1"];
+        }
+
+        private __gshared void* _handle;
+
+        shared static ~this() {
+            import core.sys.posix.dlfcn : dlclose;
+
+            if (isInitialized)
+            {
+                dlclose(_handle);
+                _handle = null;
+                isInitialized = false;
+            }
+        }
+    }
+
+    version (Windows)
+    {
+        import core.sys.windows.dbghelp : UnDecorateSymbolNameFunc;
+
+        @nogc nothrow extern(System)
+        {
+            private UnDecorateSymbolNameFunc UnDecorateSymbolName;
+        }
+    }
+
+    char[] cppdemangle(const(char)[] mangledName, char[] outputBuffer, string prefix = "") @safe
+    {
+        auto prefixEmpty = prefix.length <= 0;
+        auto demangleOffset = prefixEmpty ? 0 : prefix.length + 1; // Add prefix + space
+
+        if (outputBuffer is null)
+        {
+            return null;
+        }
+
+        if (outputBuffer.length < demangleOffset)
+        {
+            return copyResult(mangledName, outputBuffer);
+        }
+
+        auto demangle = _cppdemangle(mangledName, outputBuffer[demangleOffset..$]);
+
+        if (demangle is null)
+        {
+            return copyResult(mangledName, outputBuffer);
+        }
+
+        if (!prefixEmpty)
+        {
+            outputBuffer[0..demangleOffset - 1] = prefix;
+            outputBuffer[demangleOffset - 1] = ' ';
+        }
+
+        return outputBuffer[0..(demangle.length + demangleOffset)];
+    }
+
+    static CPPDemangleStatus initialize()
+    {
+        if (isInitialized)
+        {
+            return CPPDemangleStatus.INITIALIZED;
+        }
+
+        version (iOS)
+        {
+            // Not supported (dlopen doesn't work)
+            // Fix me
+            return CPPDemangleStatus.LOAD_ERROR;
+        }
+        else version (Posix)
+        {
+            import core.sys.posix.dlfcn : dlsym, dlopen, dlclose, RTLD_LAZY;
+
+            auto handle = dlopen(null, RTLD_LAZY);
+            assert(handle !is null);
+            auto p = dlsym(handle, "__cxa_demangle");
+
+            if (p !is null)
+            {
+                _handle = handle;
+                _instance.__cxa_demangle = cast(typeof(CPPDemangle.__cxa_demangle)) p;
+                isInitialized = true;
+                return CPPDemangleStatus.INITIALIZED;
+            }
+
+            dlclose(handle);
+
+            foreach (name; names)
+            {
+                handle = dlopen(name.ptr, RTLD_LAZY);
+
+                if (handle !is null)
+                {
+                    break;
+                }
+            }
+
+            if (handle is null)
+            {
+                return CPPDemangleStatus.LOAD_ERROR;
+            }
+
+            p = dlsym(handle, "__cxa_demangle");
+
+            if (p !is null)
+            {
+                _handle = handle;
+                _instance.__cxa_demangle = cast(typeof(CPPDemangle.__cxa_demangle)) p;
+                isInitialized = true;
+                return CPPDemangleStatus.INITIALIZED;
+            }
+            else
+            {
+                return CPPDemangleStatus.SYMBOL_ERROR;
+            }
+        }
+        else version (Windows)
+        {
+            import core.sys.windows.dbghelp : DbgHelp;
+
+            auto dbgHelp = DbgHelp.get();
+
+            if (dbgHelp is null)
+            {
+                return CPPDemangleStatus.LOAD_ERROR;
+            }
+
+            auto func = dbgHelp.UnDecorateSymbolName;
+
+            if (dbgHelp.UnDecorateSymbolName !is null)
+            {
+                _instance.UnDecorateSymbolName = dbgHelp.UnDecorateSymbolName;
+                isInitialized = true;
+                return CPPDemangleStatus.INITIALIZED;
+            }
+            else
+            {
+                return CPPDemangleStatus.SYMBOL_ERROR;
+            }
+        }
+        else
+        {
+            // Platform not supported
+            return CPPDemangleStatus.LOAD_ERROR;
+        }
+    }
+
+    static CPPDemangle instance() @nogc nothrow
+    {
+        return _instance;
+    }
+
+    private char[] _cppdemangle(const(char)[] mangledName, char[] outputBuffer) @trusted
+    {
+        import core.memory : pureCalloc, pureFree;
+        import core.stdc.string : strlen;
+
+        if (!isInitialized)
+        {
+            return null;
+        }
+
+        auto mangledNamePtr = cast(char*) pureCalloc(mangledName.length + 1, char.sizeof);
+
+        scope(exit)
+        {
+            if (mangledNamePtr !is null)
+            {
+                pureFree(mangledNamePtr);
+            }
+        }
+
+        mangledNamePtr[0..mangledName.length] = mangledName[];
+
+        version (Posix)
+        {
+            int status;
+            auto demangledName = _instance.__cxa_demangle(mangledNamePtr, null, null, &status);
+            // NOTE: Due to the implementation of __cxa_demangle, the result of the function
+            // will be a pointer to arrays of characters of unknown size before the call to
+            // the function.
+            // It is in no way possible to pass the output buffer of this function and perform
+            // the demangling if its size is sufficient directly by calling __cxa_demangle,
+            // because if the size was insufficient __cxa_demangle would try to increase
+            // it through realloc.
+            // Tto use this function safely, it is therefore necessary to allow the necessary
+            // memory to be allocated (just pass null) and then copy (if the size is sufficient)
+             // the result into the output buffer.
+
+            if (status != 0 && demangledName is null)
+            {
+                return null;
+            }
+
+            scope(exit)
+            {
+                if (demangledName !is null)
+                {
+                    pureFree(demangledName);
+                }
+            }
+
+            return copyResult(demangledName[0..strlen(demangledName)], outputBuffer);
+        }
+
+        version (Windows)
+        {
+            import core.sys.windows.windef : DWORD;
+
+            auto maxStringLen = (outputBuffer.length > DWORD.max) ? DWORD.max : cast(DWORD) outputBuffer.length;
+            // NOTE: UnDecorateSymbolName expects to receive a length in DWORD (uint) instead
+            // outputBuffer.length would be ulong.
+            // To make a safe cast I make sure not to exceed DWORD.max
+
+            auto bufferLen = _instance.UnDecorateSymbolName(mangledNamePtr, outputBuffer.ptr, maxStringLen, 0);
+
+            if (bufferLen <= 0)
+            {
+                return null;
+            }
+
+            return outputBuffer[0..bufferLen];
+        }
+    }
+}
+
+package enum CPPDemangleStatus
+{
+    INITIALIZED = 1,
+    LOAD_ERROR = -1,
+    SYMBOL_ERROR = -2
+}
+
+package char[] copyResult(const(char)[] input, char[] output) @safe @nogc nothrow
+{
+    if (input.length > output.length)
+    {
+        return null;
+    }
+
+    output[0..input.length] = input[0..input.length];
+    return output[0..input.length];
+}