G ++ problems with links: in the function `_start ': (.text + 0x20): undefined reference to` main'

Question

I get an undefined link to the main error - although I defined main and (AFAICT), I linked it correctly. Here is my code and the commands I used:

// ################################################ //proj1.h #ifndef __SCRATCH_PROJ1_H #define __SCRATCH_PROJ1_H int addOne(int i); #endif /*__SCRATCH_PROJ1_H */ // ################################################ //proj1.cpp #include "proj1.h" int addOne(int i){ return i+1; } // ################################################ //proj1_unittest.cpp #include "proj1.h" #include "gtest/gtest.h" // Test Function TEST(addOneTest, Positive) { EXPECT_EQ(1,addOne(0)); EXPECT_EQ(2,addOne(1)); EXPECT_EQ(40320, addOne(40319)); } TEST(addOneTest, Negative) { EXPECT_FALSE(addOneTest(-1)); } GTEST_API_ int main(int argc, char **argv) { testing::InitGoogleTest(&argc, argv); return RUN_ALL_TESTS(); } 

Here is the console output:

 $ g++ -isystem -pthread -c ${SOURCE_DIR}/proj1.c -o ${SOURCE_DIR}/proj1.o $ g++ -o ${SOURCE_DIR}/mytest ${SOURCE_DIR}/*.o -L${GTEST_DIR} libgtest.a /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o: In function `_start': (.text+0x20): undefined reference to `main' collect2: ld returned 1 exit status 

Why is the main() function not found by the linker?

Answer 1

As far as I can tell, you are not compiling the file proj1_unittest.cpp (as your comment on the code) /proj1_unittest.c (as follows from your output to the console).