2 * Copyright 2016 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #include <folly/Demangle.h>
22 #include <folly/Malloc.h>
23 #include <folly/portability/Config.h>
25 #if FOLLY_HAVE_CPLUS_DEMANGLE_V3_CALLBACK
30 // TODO(tudorb): Detect this with autoconf for the open-source version.
32 // __attribute__((__weak__)) doesn't work, because cplus_demangle_v3_callback
33 // is exported by an object file in libiberty.a, and the ELF spec says
34 // "The link editor does not extract archive members to resolve undefined weak
35 // symbols" (but, interestingly enough, will resolve undefined weak symbols
36 // with definitions from archive members that were extracted in order to
37 // resolve an undefined global (strong) symbol)
40 # define FOLLY_DEFINED_DMGL 1
41 # define DMGL_NO_OPTS 0 /* For readability... */
42 # define DMGL_PARAMS (1 << 0) /* Include function args */
43 # define DMGL_ANSI (1 << 1) /* Include const, volatile, etc */
44 # define DMGL_JAVA (1 << 2) /* Demangle as Java rather than C++. */
45 # define DMGL_VERBOSE (1 << 3) /* Include implementation details. */
46 # define DMGL_TYPES (1 << 4) /* Also try to demangle type encodings. */
47 # define DMGL_RET_POSTFIX (1 << 5) /* Print function return types (when
48 present) after function signature */
51 extern "C" int cplus_demangle_v3_callback(
53 int options, // We use DMGL_PARAMS | DMGL_TYPES, aka 0x11
54 void (*callback)(const char*, size_t, void*),
61 #if FOLLY_HAVE_CPLUS_DEMANGLE_V3_CALLBACK
63 fbstring demangle(const char* name) {
64 #ifdef FOLLY_DEMANGLE_MAX_SYMBOL_SIZE
65 // GCC's __cxa_demangle() uses on-stack data structures for the
66 // parser state which are linear in the number of components of the
67 // symbol. For extremely long symbols, this can cause a stack
68 // overflow. We set an arbitrary symbol length limit above which we
69 // just return the mangled name.
70 size_t mangledLen = strlen(name);
71 if (mangledLen > FOLLY_DEMANGLE_MAX_SYMBOL_SIZE) {
72 return fbstring(name, mangledLen);
78 // malloc() memory for the demangled type name
79 char* demangled = abi::__cxa_demangle(name, nullptr, &len, &status);
83 // len is the length of the buffer (including NUL terminator and maybe
85 return fbstring(demangled, strlen(demangled), len, AcquireMallocatedString());
96 void demangleCallback(const char* str, size_t size, void* p) {
97 DemangleBuf* buf = static_cast<DemangleBuf*>(p);
98 size_t n = std::min(buf->remaining, size);
99 memcpy(buf->dest, str, n);
107 size_t demangle(const char* name, char* out, size_t outSize) {
108 #ifdef FOLLY_DEMANGLE_MAX_SYMBOL_SIZE
109 size_t mangledLen = strlen(name);
110 if (mangledLen > FOLLY_DEMANGLE_MAX_SYMBOL_SIZE) {
112 size_t n = std::min(mangledLen, outSize - 1);
113 memcpy(out, name, n);
122 dbuf.remaining = outSize ? outSize - 1 : 0; // leave room for null term
125 // Unlike most library functions, this returns 1 on success and 0 on failure
126 int status = cplus_demangle_v3_callback(
128 DMGL_PARAMS | DMGL_ANSI | DMGL_TYPES,
131 if (status == 0) { // failed, return original
132 return folly::strlcpy(out, name, outSize);
142 fbstring demangle(const char* name) {
146 size_t demangle(const char* name, char* out, size_t outSize) {
147 return folly::strlcpy(out, name, outSize);
152 size_t strlcpy(char* dest, const char* const src, size_t size) {
153 size_t len = strlen(src);
155 size_t n = std::min(len, size - 1); // always null terminate!
156 memcpy(dest, src, n);