Sample code:

#include 
      
       #include 
       
        extern void foo() __attribute__((weak));int main() {  if (foo) foo();  printf("this is a test\n");}
       
      

Compile command:

gcc -H -v sample.c

Compile options:

-H tells you that the right include files used.

Official document:

Print the name of each header file used, in addition to other normal

activities. Each name is indented to show how deep in the ‘#include’

stack it is. Precompiled header files are also printed, even if they

are found to be invalid; an invalid precompiled header file is printed

with ‘…x’ and a valid one with ‘…!’ .

-v (or even maybe -Wl,-v) tells you that the right libraries used.

Official document:

Print (on standard error output) the commands executed to run the

stages of compilation. Also print the version number of the compiler

driver program and of the preprocessor and the compiler proper.

Sample output:

…………………….

/usr/include/x86_64-linux-gnu/bits/waitflags.h

/usr/include/x86_64-linux-gnu/bits/waitstatus.h

/usr/include/x86_64-linux-gnu/gnu/stubs-64.h

/usr/include/x86_64-linux-gnu/gnu/stubs.h COLLECT_GCC_OPTIONS=’-o’

‘hello’ ‘-H’ ‘-v’ ‘-mtune=generic’ ‘-march=x86-64’ as -v –64 -o

/tmp/ccwD1DYA.o /tmp/cc8CU0IV.s GNU assembler version 2.24

(x86_64-linux-gnu) using BFD version (GNU Binutils for Ubuntu) 2.24

COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/

LIBRARY_PATH=/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/4.8/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/lib/:./:/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../:/lib/:/usr/lib/

…………..

Ref: