> I have copied gcc output of a simple C program as follows. > COLLECT_GCC_OPTIONS has been repeated 3 times. Does it mean the > compilation has 3 passes? Mhhhh, a kind of. COLLECT_GCC_OPTIONS is just an environment variable which is passed to all GCC sub-processes (compiler, assembler, linker) and its value is just repeated before each sub-process invocation. > Which of them is considered for compilation and when? See the description of the different phases below. > as -V -Qy -o /tmp/ccb2pBgG.o /tmp/ccQNR8AL.s This is the invocation of the assembler (e.g. GNU assembler from the binutils package) A short explanation of the output: [GCC DRIVER] > Using built-in specs. > Target: i686-redhat-linux > Configured with: ../configure --prefix=/usr --mandir=/usr/share/man > --infodir=/usr/share/info > --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-bootstrap > --enable-shared --enable-threads=posix --enable-checking=release > --with-system-zlib --enable-__cxa_atexit > --disable-libunwind-exceptions --enable-gnu-unique-object > --enable-languages=c,c++,objc,obj-c++,java,fortran,ada > --enable-java-awt=gtk --disable-dssi --enable-plugin > --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre > --enable-libgcj-multifile --enable-java-maintainer-mode > --with-ecj-jar=/usr/share/java/eclipse-ecj.jar > --disable-libjava-multilib --with-ppl --with-cloog --with-tune=generic > --with-arch=i686 --build=i686-redhat-linux > Thread model: posix > gcc version 4.4.2 20091222 (Red Hat 4.4.2-20) (GCC) > COLLECT_GCC_OPTIONS='-v' '-o' 'prog1' '-mtune=generic' '-march=i686' [Invocation of the compiler proper, cc1] > /usr/libexec/gcc/i686-redhat-linux/4.4.2/cc1 -quiet -v prog1.c -quiet > -dumpbase prog1.c -mtune=generic -march=i686 -auxbase prog1 -version > -o /tmp/ccQNR8AL.s [COMPILER OUTPUT] > ignoring nonexistent directory > "/usr/lib/gcc/i686-redhat-linux/4.4.2/include-fixed" > ignoring nonexistent directory > "/usr/lib/gcc/i686-redhat-linux/4.4.2/../../../../i686-redhat-linux/include" > #include "..." search starts here: > #include <...> search starts here: > /usr/local/include > /usr/lib/gcc/i686-redhat-linux/4.4.2/include > /usr/include > End of search list. > GNU C (GCC) version 4.4.2 20091222 (Red Hat 4.4.2-20) (i686-redhat-linux) > compiled by GNU C version 4.4.2 20091222 (Red Hat 4.4.2-20), GMP > version 4.3.1, MPFR version 2.4.1. > GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 > Compiler executable checksum: ce871bdaf8715137a79dafbeccd13c96 [GCC DRIVER] > COLLECT_GCC_OPTIONS='-v' '-o' 'prog1' '-mtune=generic' '-march=i686' [Assembler invocation] > as -V -Qy -o /tmp/ccb2pBgG.o /tmp/ccQNR8AL.s > GNU assembler version 2.19.51.0.14 (i686-redhat-linux) using BFD > version version 2.19.51.0.14-34.fc12 20090722 [GCC DRIVER] > COMPILER_PATH=/usr/libexec/gcc/i686-redhat-linux/4.4.2/:/usr/libexec/gcc/i686-redhat-linux/4.4.2/:/usr/libexec/gcc/i686-redhat-linux/:/usr/lib/gcc/i686-redhat-linux/4.4.2/:/usr/lib/gcc/i686-redhat-linux/:/usr/libexec/gcc/i686-redhat-linux/4.4.2/:/usr/libexec/gcc/i686-redhat-linux/:/usr/lib/gcc/i686-redhat-linux/4.4.2/:/usr/lib/gcc/i686-redhat-linux/ > LIBRARY_PATH=/usr/lib/gcc/i686-redhat-linux/4.4.2/:/usr/lib/gcc/i686-redhat-linux/4.4.2/:/usr/lib/gcc/i686-redhat-linux/4.4.2/../../../:/lib/:/usr/lib/ > COLLECT_GCC_OPTIONS='-v' '-o' 'prog1' '-mtune=generic' '-march=i686' [Invocation of collect2, which usually calls the linker 'ld'] > /usr/libexec/gcc/i686-redhat-linux/4.4.2/collect2 --eh-frame-hdr > --build-id -m elf_i386 --hash-style=gnu -dynamic-linker > /lib/ld-linux.so.2 -o prog1 > /usr/lib/gcc/i686-redhat-linux/4.4.2/../../../crt1.o > /usr/lib/gcc/i686-redhat-linux/4.4.2/../../../crti.o > /usr/lib/gcc/i686-redhat-linux/4.4.2/crtbegin.o > -L/usr/lib/gcc/i686-redhat-linux/4.4.2 > -L/usr/lib/gcc/i686-redhat-linux/4.4.2 > -L/usr/lib/gcc/i686-redhat-linux/4.4.2/../../.. /tmp/ccb2pBgG.o -lgcc > --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s > --no-as-needed /usr/lib/gcc/i686-redhat-linux/4.4.2/crtend.o > /usr/lib/gcc/i686-redhat-linux/4.4.2/../../../crtn.o > ------------------------------------------- Though, you got in total 3 phases which all get called by compiler driver program 'gcc': * compiler: cc1 * assembler: as * linker: collect2/ld Andi
