(gccint.info.gz) Collect2

 
 20 `collect2'
 *************
 
 GCC uses a utility called `collect2' on nearly all systems to arrange
 to call various initialization functions at start time.
 
  The program `collect2' works by linking the program once and looking
 through the linker output file for symbols with particular names
 indicating they are constructor functions.  If it finds any, it creates
 a new temporary `.c' file containing a table of them, compiles it, and
 links the program a second time including that file.
 
  The actual calls to the constructors are carried out by a subroutine
 called `__main', which is called (automatically) at the beginning of
 the body of `main' (provided `main' was compiled with GNU CC).  Calling
 `__main' is necessary, even when compiling C code, to allow linking C
 and C++ object code together.  (If you use `-nostdlib', you get an
 unresolved reference to `__main', since it's defined in the standard
 GCC library.  Include `-lgcc' at the end of your compiler command line
 to resolve this reference.)
 
  The program `collect2' is installed as `ld' in the directory where the
 passes of the compiler are installed.  When `collect2' needs to find
 the _real_ `ld', it tries the following file names:
 
    * `real-ld' in the directories listed in the compiler's search
      directories.
 
    * `real-ld' in the directories listed in the environment variable
      `PATH'.
 
    * The file specified in the `REAL_LD_FILE_NAME' configuration macro,
      if specified.
 
    * `ld' in the compiler's search directories, except that `collect2'
      will not execute itself recursively.
 
    * `ld' in `PATH'.
 
  "The compiler's search directories" means all the directories where
 `gcc' searches for passes of the compiler.  This includes directories
 that you specify with `-B'.
 
  Cross-compilers search a little differently:
 
    * `real-ld' in the compiler's search directories.
 
    * `TARGET-real-ld' in `PATH'.
 
    * The file specified in the `REAL_LD_FILE_NAME' configuration macro,
      if specified.
 
    * `ld' in the compiler's search directories.
 
    * `TARGET-ld' in `PATH'.
 
  `collect2' explicitly avoids running `ld' using the file name under
 which `collect2' itself was invoked.  In fact, it remembers up a list
 of such names--in case one copy of `collect2' finds another copy (or
 version) of `collect2' installed as `ld' in a second place in the
 search path.
 
  `collect2' searches for the utilities `nm' and `strip' using the same
 algorithm as above for `ld'.
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