Using Memory Sanitizer instrumented libc++ - c++

Question

I have built an instrumented libc++ as described here. I have set the flags as the above site suggests:
MSAN_CFLAGS="-fsanitize=memory -stdlib=libc++ -L/path_to/llvm-build-msan/lib -lc++abi -I/path_to/llvm-build-msan/include -I/path_to/llvm-build-msan/include/c++/v1"
and tried to build this:
#include <string.h>
#include <stdio.h>
int main(){
char str[] = "This is a sample string";
char * pch;
printf ("Looking for the 's' character in \"%s\"...\n",str);
pch=strchr(str,'s');
}
with: clang++ ${MSAN_CFLAGS} m.cpp. I got:
In file included from m.cpp:1:
/path_to/llvm-build-msan/include/c++/v1/string.h:74:64: error: use of undeclared identifier 'strchr'
char* __libcpp_strchr(const char* __s, int __c) {return (char*)strchr(__s, __c);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:81:75: error: use of undeclared identifier 'strpbrk'
char* __libcpp_strpbrk(const char* __s1, const char* __s2) {return (char*)strpbrk(__s1, __s2);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:88:65: error: use of undeclared identifier 'strrchr'; did you mean 'strchr'?
char* __libcpp_strrchr(const char* __s, int __c) {return (char*)strrchr(__s, __c);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:76:13: note: 'strchr' declared here
const char* strchr(const char* __s, int __c) {return __libcpp_strchr(__s, __c);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:95:49: error: unknown type name 'size_t'
void* __libcpp_memchr(const void* __s, int __c, size_t __n) {return (void*)memchr(__s, __c, __n);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:97:46: error: unknown type name 'size_t'
const void* memchr(const void* __s, int __c, size_t __n) {return __libcpp_memchr(__s, __c, __n);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:99:46: error: unknown type name 'size_t'
void* memchr( void* __s, int __c, size_t __n) {return __libcpp_memchr(__s, __c, __n);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:102:74: error: use of undeclared identifier 'strstr'; did you mean 'strchr'?
char* __libcpp_strstr(const char* __s1, const char* __s2) {return (char*)strstr(__s1, __s2);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:78:13: note: 'strchr' declared here
char* strchr( char* __s, int __c) {return __libcpp_strchr(__s, __c);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:102:74: error: no matching function for call to 'strchr'
char* __libcpp_strstr(const char* __s1, const char* __s2) {return (char*)strstr(__s1, __s2);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:78:13: note: candidate disabled: <no message provided>
char* strchr( char* __s, int __c) {return __libcpp_strchr(__s, __c);}
^
/path_to/llvm-build-msan/include/c++/v1/string.h:102:81: error: cannot initialize a parameter of type 'char *' with an lvalue of type 'const char *'
char* __libcpp_strstr(const char* __s1, const char* __s2) {return (char*)strstr(__s1, __s2);}
^~~~
/path_to/llvm-build-msan/include/c++/v1/string.h:78:32: note: passing argument to parameter '__s' here
char* strchr( char* __s, int __c) {return __libcpp_strchr(__s, __c);}
^
m.cpp:7:5: error: use of undeclared identifier 'printf'
printf ("Looking for the 's' character in \"%s\"...\n",str);
^
10 errors generated.
I also tried to build a memory sanitized clang++ using the same method as to build libc++, but I got:
[ 9%] Building Checkers.inc...
==20994==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x53bf93 in _M_lower_bound /usr/bin/../lib/gcc/x86_64-linux-gnu/7.2.0/../../../../include/c++/7.2.0/bits/stl_tree.h:1887:7
#1 0x53bf93 in std::_Rb_tree<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::unique_ptr<llvm::Record, std::default_delete<llvm::Record> > >, std::_Select1st<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::unique_ptr<llvm::Record, std::default_delete<llvm::Record> > > >, std::less<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const, std::unique_ptr<llvm::Record, std::default_delete<llvm::Record> > > > >::find(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const /usr/bin/../lib/gcc/x86_64-linux-gnu/7.2.0/../../../../include/c++/7.2.0/bits/stl_tree.h:2536
#2 0x6f0f32 in find /usr/bin/../lib/gcc/x86_64-linux-gnu/7.2.0/../../../../include/c++/7.2.0/bits/stl_map.h:1174:21
#3 0x6f0f32 in getClass /path_to/llvm/include/llvm/TableGen/Record.h:1536
#4 0x6f0f32 in llvm::TGParser::ParseClass() /path_to/llvm/lib/TableGen/TGParser.cpp:2130
#5 0x6f0924 in llvm::TGParser::ParseObject(llvm::MultiClass*) /path_to/llvm/lib/TableGen/TGParser.cpp:2669:29
#6 0x6fc77a in ParseObjectList /path_to/llvm/lib/TableGen/TGParser.cpp:2678:9
#7 0x6fc77a in llvm::TGParser::ParseFile() /path_to/llvm/lib/TableGen/TGParser.cpp:2686
#8 0x688049 in llvm::TableGenMain(char*, bool (*)(llvm::raw_ostream&, llvm::RecordKeeper&)) /path_to/llvm/lib/TableGen/Main.cpp:96:14
#9 0x61b5d5 in main /path_to/llvm/tools/clang/utils/TableGen/TableGen.cpp:287:10
#10 0x7f03af5691c0 in __libc_start_main /build/glibc-CxtIbX/glibc-2.26/csu/../csu/libc-start.c:308
#11 0x424d99 in _start (/path_to/llvm-build/bin/clang-tblgen+0x424d99)
SUMMARY: MemorySanitizer: use-of-uninitialized-value /usr/bin/../lib/gcc/x86_64-linux-gnu/7.2.0/../../../../include/c++/7.2.0/bits/stl_tree.h:1887:7 in _M_lower_bound
Exiting
tools/clang/include/clang/StaticAnalyzer/Checkers/CMakeFiles/ClangSACheckers.dir/build.make:94: recipe for target 'tools/clang/include/clang/StaticAnalyzer/Checkers/Checkers.inc.tmp' failed
make[3]: *** [tools/clang/include/clang/StaticAnalyzer/Checkers/Checkers.inc.tmp] Error 77
CMakeFiles/Makefile2:18275: recipe for target 'tools/clang/include/clang/StaticAnalyzer/Checkers/CMakeFiles/ClangSACheckers.dir/all' failed
make[2]: *** [tools/clang/include/clang/StaticAnalyzer/Checkers/CMakeFiles/ClangSACheckers.dir/all] Error 2
make[2]: *** Waiting for unfinished jobs....
Any suggestions how to compile the above code?
Of course, clang++ m.cpp works, but in this case the executable is linked to libstdc++.

Answer 1

Found the solution here:
compile with uninstrumented clang with -fsanitize=memory
link with the above MSAN_CFLAGS (you can omit the include paths), adding -Wl,-rpath -Wl,/path_to/llvm-build-msan/lib/