Under Ubuntu 14.10, I got this error, which prevents building:

g++ -Wall -L. -lstdc++ -lmsr605 MSR605.cpp -o msr605.o
In file included from MSR605.cpp:27:0:
msr605.h:65:1: warning: 'typedef' was ignored in this declaration
};
^
msr605.h:71:1: warning: 'typedef' was ignored in this declaration
};
^
MSR605.cpp: In function 'void printTrack(const char_, unsigned char_, unsigned int)':
MSR605.cpp:47:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int x = 0; x < len; x++) printf("%02x", buf[x]);
^
MSR605.cpp: In function 'void printTrackiso(const char_, unsigned char_, unsigned int)':
MSR605.cpp:55:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int x = 0; x < len; x++) printf("%c", buf[x]);
^
MSR605.cpp: In function 'int main(int, const char* const_)':
MSR605.cpp:93:22: warning: deprecated conversion from string constant to 'char_' [-Wwrite-strings]
msr->connect(DEVICE);
^
/tmp/ccJDGv3q.o: In function sigproc(int)': MSR605.cpp:(.text+0x26): undefined reference toMSR605::disconnect()'
MSR605.cpp:(.text+0x3a): undefined reference to MSR605::~MSR605()' /tmp/ccJDGv3q.o: In functionmain':
MSR605.cpp:(.text+0x293): undefined reference to MSR605::connect(char*)' MSR605.cpp:(.text+0x2b6): undefined reference toMSR605::sendReset()'
MSR605.cpp:(.text+0x2c5): undefined reference to MSR605::getFirmware()' MSR605.cpp:(.text+0x2d4): undefined reference toMSR605::getModel()'
MSR605.cpp:(.text+0x2e3): undefined reference to MSR605::sendReset()' MSR605.cpp:(.text+0x2f2): undefined reference toMSR605::init()'
MSR605.cpp:(.text+0x30b): undefined reference to MSR605::setAllLEDOff()' MSR605.cpp:(.text+0x348): undefined reference toMSR605::readCard_raw(char, char, char)'
MSR605.cpp:(.text+0x3c2): undefined reference to MSR605::readCard_iso(char, char, char)' MSR605.cpp:(.text+0x430): undefined reference toMSR605::free_ms_data(magnetic_stripe_t_)'
MSR605.cpp:(.text+0x43d): undefined reference to MSR605::~MSR605()' /tmp/ccJDGv3q.o: In function__static_initialization_and_destruction_0(int, int)':
MSR605.cpp:(.text+0x4fc): undefined reference to `MSR605::MSR605()'
collect2: error: ld returned 1 exit status
Makefile:7: recipe for target 'msr605.o' failed
make: *_* [msr605.o] Error 1