std::to_string is not declared compile error in aix - c++

Question

I am compiling my code in AIX env.. it givs me error "std::to_string" is not declared
successfully compiled same code in Windows.
define LOG_MSG(message) CLogManager::LogMessage(CLogManager::CurrentDateTime() + " - " + std::string(__FILE__) + "[" + std::to_string(static_cast<_ULonglong>(__LINE__)) + "] : " + std::string(message) + "\n")
This is the macro and i am using this as
LOG_MSG(" ** BEGIN StorePasswordFromFile()");
This macro is for logging purpose

Answer 1

I'm not sure how much support the latest xlC 14.1 (or whatever version you're using) has for std::to_string().
If the support is incomplete, C has a hideous double macro method (a) of turning __LINE__ into a C-string so that you can just use std::string, the same as you have for the __FILE__ and message items, and it appears the C++ pre-processor has stayed faithful to its hideous roots :-)
The code:
#include <stdio.h>
#define STR1(x) # x
#define STR2(x) STR1(x)
int main(void) {
char x[] = __FILE__;
char y[] = STR2(__LINE__);
printf("file = %s, line = %s\n",x,y);
return 0;
}
outputs:
file = qq.c, line = 6
showing that the __LINE__ has been successfully morphed into a C-string value.
You should be able to use a similar method in your macro:
#define STR1(x) # x
#define STR2(x) STR1(x)
#define LOG_MSG(message) CLogManager::LogMessage( \
CLogManager::CurrentDateTime() + " - " + \
std::string(__FILE__) + "[" + \
std::string(STR2(__LINE__)) + "] : " + \
std::string(message) + "\n")
int main() {
LOG_MSG ("My hovercraft is full of eels");
return 0;
}
Pre-processing that with g++ -E qq.cpp gives you:
CLogManager::LogMessage( CLogManager::CurrentDateTime() + " - " + std::string("qq.cpp") + "[" + std::string("10") + "] : " + std::string("My hovercraft is full of eels") + "\n");
(showing relevant line only) which seems to match what you want.
As a side note however, since you seem to be okay adding C-strings like "[" without needing to construct strings explicitly, I'm not sure that you need the std::string() calls at all for those. You still need the C macro hack to turn the integer into a C-string but, once that's been done, you should just be able to use that as-is.
Changing the final macro to:
#define LOG_MSG(message) CLogManager::LogMessage( \
CLogManager::CurrentDateTime() + " - " + \
__FILE__ + "[" + \
STR2(__LINE__) + "] : " + \
message + "\n")
will give you:
CLogManager::LogMessage( CLogManager::CurrentDateTime() + " - " + "qq.cpp" + "[" + "10" + "] : " + "My hovercraft is full of eels" + "\n");
Whether that's a good idea, I'll leave to the wider community but it at least gets around your immediate problem. I'd probably place the whole lot inside an #if/#else/#endif so that C++11 compilers that know about std::to_string() can use the more accepted approach.
(a) If you're interested in why this works, I'll explain below.
The # and ## macro operators actually take precedence over the recursive nature of macro replacement, as per C11 6.10.3.4 /1:
After all parameters in the replacement list have been substituted and # and ##
processing has taken place, all placemarker preprocessing tokens are removed. The
resulting preprocessing token sequence is then rescanned, along with all subsequent
preprocessing tokens of the source file, for more macro names to replace.
That means that the code:
#define STR(x) # x
STR(__LINE__)
will actually result in "__LINE__" because the # happens first and, once that's happened, the __LINE__ within the string literal is not subject to further replacement. By doing the two-step process:
#define STR1(x) # x
#define STR2(x) STR1(x)
STR2(__LINE__)
the first level of replacement turns STR2(__LINE__) into STR1(3) because __LINE__ on its own is subject to expansion.
Then the second level turns STR1(3), via # 3, into "3".
Perhaps the following may help:
#define STR1(x) # x
#define STR2a(x) STRn(x)
#define STR2b(x) STR1(x)
STR1(__LINE__)
STR2a(__LINE__)
STR2b(__LINE__)
The output of that, annotated, is:
"__LINE__" - stringise, no further processing of __LINE__ inside literal.
STRn(6) - shows first stage of replacement, line number replacement.
"7" - shows full process.