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9.3 Verbose compilation

The -v option can also be used to display detailed information about the exact sequence of commands used to compile and link a program. Here is an example which shows the verbose compilation of the Hello World program:

$ gcc -v -Wall hello.c
Reading specs from /usr/lib/gcc-lib/i686/3.3.1/specs
Configured with: ../configure --prefix=/usr
Thread model: posix
gcc version 3.3.1
 /usr/lib/gcc-lib/i686/3.3.1/cc1 -quiet -v -D__GNUC__=3 
 -D__GNUC_MINOR__=3 -D__GNUC_PATCHLEVEL__=1 
 hello.c -quiet -dumpbase hello.c -auxbase hello -Wall
 -version -o /tmp/cceCee26.s
GNU C version 3.3.1 (i686-pc-linux-gnu)
 compiled by GNU C version 3.3.1 (i686-pc-linux-gnu)
GGC heuristics: --param ggc-min-expand=51 
 --param ggc-min-heapsize=40036
ignoring nonexistent directory "/usr/i686/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/include
 /usr/lib/gcc-lib/i686/3.3.1/include
 /usr/include
End of search list.
 as -V -Qy -o /tmp/ccQynbTm.o /tmp/cceCee26.s
GNU assembler version 2.12.90.0.1 (i386-linux)
using BFD version 2.12.90.0.1 20020307 Debian/GNU
Linux
/usr/lib/gcc-lib/i686/3.3.1/collect2
 --eh-frame-hdr -m elf_i386 -dynamic-linker
 /lib/ld-linux.so.2 /usr/lib/crt1.o /usr/lib/crti.o
 /usr/lib/gcc-lib/i686/3.3.1/crtbegin.o
 -L/usr/lib/gcc-lib/i686/3.3.1
 -L/usr/lib/gcc-lib/i686/3.3.1/../../.. /tmp/ccQynbTm.o
 -lgcc -lgcc_eh -lc -lgcc -lgcc_eh
 /usr/lib/gcc-lib/i686/3.3.1/crtend.o
 /usr/lib/crtn.o

The output produced by -v can be useful whenever there is a problem with the compilation process itself. It displays the full directory paths used to search for header files and libraries, the predefined preprocessor symbols, and the object files and libraries used for linking.