Pointer and address Post: 302804453

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Top Forums Programming Pointer and address Post 302804453 by alister on Wednesday 8th of May 2013 03:24:18 PM

05-08-2013

Registered User

To the OP:
If what follows confuses the issue, please ignore it. It's not critical to what you are dealing with at the moment.

Quote:

Originally Posted by DGPickett

The address in pointer argv points to memory containing an array of pointers, each pointing to memory containing a character array, except the last (highest) pointer in the array is null." ... The argv pointer is stored on the call stack as a parameter, first bit of memory, points to the array of pointers, second bit of memory, and if there are, say, 5 pointers in the array, 4 point to additional areas of memory with null terminated character arrays, and the 5th, highest is set to zeros (null). For instance, &argv might be 0xFFFFE078, containing a heap address 0x00031244, and the array of pointers is in 0x00031244-57 inclusive. The first pointer in 0x00031244-7 might be 0x00030711. The first character array may occupy 0x00030711-5, loaded with "haha", 4 char and a null.

If you'll pardon a few nits ...

The null pointer is not required to be all zeroes. Its representation is implementation defined. Further, null pointers to different types are allowed to have different internal represenations (even though a zero in source code in a pointer context is always converted to the correct internal representation for a null pointer of that type).

You mention argv pointing to the heap. You did not state that this is invariably the case, nor is it my intention to imply that you did. However, I wanted to mention that main's arguments and the environment can be found above the stack (at least on Linux and *BSD x86/amd64). On all of my systems, heap < stack < argv.

A typical result from a 32-bit x86 Linux system:

Code:

heap: 0x804a000
stack: 0xbf9023ac
argv: 0xbf9023d4

I would be genuinely interested in knowing if some of the proprietary unices (Solaris, HP-UX, AIX, etc) do things differently, but such posts would muddle the OP's thread. If you (or anyone else) are interested, please visit https://www.unix.com/unix-advanced-ex...thou-argv.html

Regards,
Alister

alister

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LEARN ABOUT DEBIAN

qd-config

QD-CONFIGG(1)															     QD-CONFIGG(1)

NAME

       qd-config - determine flags for compilation and linking

SYNOPSIS

       qd-config [options]

DESCRIPTION

       To  link  a  Fortran-90 program with the C++ qd library, it is recommended to link with the C++ compiler used to generate the library.  The
       Fortran 90 interface (along with a C-style main function calling f_main) is found in the qdmod library.	The qd-config script can  be  used
       to determine which flags to pass to compile and link your programs.

OPTIONS

       --src  Switch between source and system location.

       --prefix
	      Output configured prefix value.

       --exec-prefix
	      Output configured exec_prefix value.

       --build-flags
	      Compiler options used during build.

       --build-libs
	      Linker options used during build.

       --configure-args
	      Configure arguments used for build.

       --cxx  C++ compiler.

       --cflags
	      C++ preprocessor and compiler options.

       --cxxflags
	      C++ compiler options.

       --libs-la
	      C++ linker options and libtool archive location.

       --libs C++ linker options.

       --fc   Fortran compiler.

       --fcflags
	      Fortran compiler options.

       --fclibs
	      Fortran linker options.

       --fmainlib
	      C++ linker options for main program written in Fortran.

       --version
	      Output version.

AUTHOR

       This manual page was written by Daniel Leidert <daniel.leidert@wgdd.de> for the Debian project (but may be used by others).

User Commands							    2008-05-11							     QD-CONFIGG(1)

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