CODEWITHSUNDEEP
c++linkerincludeldinclude-path
John Haberstroh
John Haberstroh

Reputation: 505

g++ encounters a fatal error linking to crt1.o in function __start

I have been trying to compile and link Qt5, which means I have been messing with some ldconfig and include path defaults that I don't completely understand. I will do my best to limit my question to a very specific one, as my priority is fixing my compiler.

I have used a command to try 

`gcc -print-prog-name=cc1plus` -v
ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../x86_64-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/c++/4.7
 /usr/include/c++/4.7/x86_64-linux-gnu
 /usr/include/c++/4.7/backward
 /usr/lib/gcc/x86_64-linux-gnu/4.7/include
 /usr/local/include
 /usr/lib/gcc/x86_64-linux-gnu/4.7/include-fixed
 /usr/include
End of search list.

There is a problematic line at the beginning, about ignoring a non-existent directory when searching for the header. Unfortunately, this is exactly where g++ thinks it's a good idea to look for crt1.o, which I assume is some sort of binary that morphs the main() function into an executable:

g++  -Isrc  --std=c++11 -g  -c -o src/tissuecell.o src/tissuecell.cpp
g++  -Isrc  --std=c++11 -g  -c -o src/analyze.o src/analyze.cpp
g++ -o TissueCells src/tissuecell.o src/analyze.o

/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../x86_64-linux-gnu/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status

My compiler has not done this until a few hours ago (previously, it would compile!), and what comes to mind in terms of "irreversible commands" that I typed was a single:

sudo ldconfig

Can anyone get me out of this terrible pit of linking and compilation problems, and remove this pesky line from my include path?

Some questions that you might also be able to answer that would make me very happy:

Upvotes: 2

Views: 5106

Answers (2)

John Haberstroh
John Haberstroh

Reputation: 505

Oh gosh, this is embarrassing. My problem was that I did not fix my Makefile after giving up on the new build; the error was coming from a lack of main() function in my codebase.

The following command allowed me to test my compiler for internal errors: 

echo "int main() { return 0; }" > /tmp/test.c; gcc -v /tmp/test.c

I pulled back to an old commit on my git, and got my code to compile, which served as a good double-check on my compiler's sanity.

Upvotes: 3

fghj
fghj

Reputation: 9404

First of all you can run gcc(g++) with "-v" option, for example:

echo "int main() { return 0; }" > /tmp/test.c
gcc -v /tmp/test.c

You find in ouput the things like:

--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.3/include/g++-v4

plus 

#include <...> search starts here:
 /usr/lib/gcc/x86_64-pc-linux-gnu/4.7.3/include
 /usr/lib/gcc/x86_64-pc-linux-gnu/4.7.3/include-fixed
 /usr/include

LIBRARY_PATH=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.3/:/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.3/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.3/../../../../x86_64-pc-linux-gnu/lib/:/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.3/../../../:/lib/:/usr/lib/

and many other stuff.

The second variant you can use "strace -f" in front of your command, grep ouput with pattern open to find out where and what file is used.

Upvotes: 2

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