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view content of .obj file generated by MSVC compiler ?

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  • J jsulm
    15 Feb 2022, 12:20

    @Vinoth-Rajendran4 See https://www.geeksforgeeks.org/memory-layout-of-c-program/

    V Offline
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    Vinoth Rajendran4
    wrote on 15 Feb 2022, 12:58 last edited by
    #8

    @jsulm : memory layout, i am aware.
    But like to know, if we could see the value of static variable in object file ?

    J 1 Reply Last reply 15 Feb 2022, 13:15
    0
    • V Vinoth Rajendran4
      15 Feb 2022, 12:58

      @jsulm : memory layout, i am aware.
      But like to know, if we could see the value of static variable in object file ?

      J Offline
      J Offline
      jsulm
      Lifetime Qt Champion
      wrote on 15 Feb 2022, 13:15 last edited by
      #9

      @Vinoth-Rajendran4 said in view content of .obj file generated by MSVC compiler ?:

      if we could see the value of static variable in object file ?

      Of couse you can - use a hex editor.
      See "4. Let us initialize the static variable which will then be stored in the Data Segment (DS)" in the link I provided.

      https://forum.qt.io/topic/113070/qt-code-of-conduct

      1 Reply Last reply
      1
      • K Offline
        K Offline
        Kent-Dorfman
        wrote on 17 Feb 2022, 21:16 last edited by
        #10
        NM(1)                                                                                                      GNU Development Tools                                                                                                     NM(1)
        
        NAME
               nm - list symbols from object files
        
        SYNOPSIS
               nm [-A|-o|--print-file-name] [-a|--debug-syms]
                  [-B|--format=bsd] [-C|--demangle[=style]]
                  [-D|--dynamic] [-fformat|--format=format]
                  [-g|--extern-only] [-h|--help]
                  [-l|--line-numbers] [--inlines]
                  [-n|-v|--numeric-sort]
                  [-P|--portability] [-p|--no-sort]
                  [-r|--reverse-sort] [-S|--print-size]
                  [-s|--print-armap] [-t radix|--radix=radix]
                  [-u|--undefined-only] [-V|--version]
                  [-X 32_64] [--defined-only] [--no-demangle]
                  [--plugin name]
                  [--no-recurse-limit|--recurse-limit]]
                  [--size-sort] [--special-syms]
                  [--synthetic] [--with-symbol-versions] [--target=bfdname]
                  [objfile...]
        
        DESCRIPTION
               GNU nm lists the symbols from object files objfile....  If no object files are listed as arguments, nm assumes the file a.out.
        
               For each symbol, nm shows:
        
               ·   The symbol value, in the radix selected by options (see below), or hexadecimal by default.
        
               ·   The symbol type.  At least the following types are used; others are, as well, depending on the object file format.  If lowercase, the symbol is usually local; if uppercase, the symbol is global (external).  There are
                   however a few lowercase symbols that are shown for special global symbols ("u", "v" and "w").
        
                   "A" The symbol's value is absolute, and will not be changed by further linking.
        
                   "B"
                   "b" The symbol is in the BSS data section.  This section typically contains zero-initialized or uninitialized data, although the exact behavior is system dependent.
        
                   "C" The symbol is common.  Common symbols are uninitialized data.  When linking, multiple common symbols may appear with the same name.  If the symbol is defined anywhere, the common symbols are treated as undefined
                       references.
        
                   "D"
                   "d" The symbol is in the initialized data section.
        
                   "G"
                   "g" The symbol is in an initialized data section for small objects.  Some object file formats permit more efficient access to small data objects, such as a global int variable as opposed to a large global array.
        
                   "i" For PE format files this indicates that the symbol is in a section specific to the implementation of DLLs.  For ELF format files this indicates that the symbol is an indirect function.  This is a GNU extension to the
                       standard set of ELF symbol types.  It indicates a symbol which if referenced by a relocation does not evaluate to its address, but instead must be invoked at runtime.  The runtime execution will then return the value to
                       be used in the relocation.
        
                   "I" The symbol is an indirect reference to another symbol.
        
                   "N" The symbol is a debugging symbol.
        
                   "p" The symbols is in a stack unwind section.
        
                   "R"
                   "r" The symbol is in a read only data section.
        
                   "S"
                   "s" The symbol is in an uninitialized or zero-initialized data section for small objects.
        
        
        
        J V 2 Replies Last reply 17 Feb 2022, 21:53
        1
        • K Kent-Dorfman
          17 Feb 2022, 21:16
          NM(1)                                                                                                      GNU Development Tools                                                                                                     NM(1)
          
          NAME
                 nm - list symbols from object files
          
          SYNOPSIS
                 nm [-A|-o|--print-file-name] [-a|--debug-syms]
                    [-B|--format=bsd] [-C|--demangle[=style]]
                    [-D|--dynamic] [-fformat|--format=format]
                    [-g|--extern-only] [-h|--help]
                    [-l|--line-numbers] [--inlines]
                    [-n|-v|--numeric-sort]
                    [-P|--portability] [-p|--no-sort]
                    [-r|--reverse-sort] [-S|--print-size]
                    [-s|--print-armap] [-t radix|--radix=radix]
                    [-u|--undefined-only] [-V|--version]
                    [-X 32_64] [--defined-only] [--no-demangle]
                    [--plugin name]
                    [--no-recurse-limit|--recurse-limit]]
                    [--size-sort] [--special-syms]
                    [--synthetic] [--with-symbol-versions] [--target=bfdname]
                    [objfile...]
          
          DESCRIPTION
                 GNU nm lists the symbols from object files objfile....  If no object files are listed as arguments, nm assumes the file a.out.
          
                 For each symbol, nm shows:
          
                 ·   The symbol value, in the radix selected by options (see below), or hexadecimal by default.
          
                 ·   The symbol type.  At least the following types are used; others are, as well, depending on the object file format.  If lowercase, the symbol is usually local; if uppercase, the symbol is global (external).  There are
                     however a few lowercase symbols that are shown for special global symbols ("u", "v" and "w").
          
                     "A" The symbol's value is absolute, and will not be changed by further linking.
          
                     "B"
                     "b" The symbol is in the BSS data section.  This section typically contains zero-initialized or uninitialized data, although the exact behavior is system dependent.
          
                     "C" The symbol is common.  Common symbols are uninitialized data.  When linking, multiple common symbols may appear with the same name.  If the symbol is defined anywhere, the common symbols are treated as undefined
                         references.
          
                     "D"
                     "d" The symbol is in the initialized data section.
          
                     "G"
                     "g" The symbol is in an initialized data section for small objects.  Some object file formats permit more efficient access to small data objects, such as a global int variable as opposed to a large global array.
          
                     "i" For PE format files this indicates that the symbol is in a section specific to the implementation of DLLs.  For ELF format files this indicates that the symbol is an indirect function.  This is a GNU extension to the
                         standard set of ELF symbol types.  It indicates a symbol which if referenced by a relocation does not evaluate to its address, but instead must be invoked at runtime.  The runtime execution will then return the value to
                         be used in the relocation.
          
                     "I" The symbol is an indirect reference to another symbol.
          
                     "N" The symbol is a debugging symbol.
          
                     "p" The symbols is in a stack unwind section.
          
                     "R"
                     "r" The symbol is in a read only data section.
          
                     "S"
                     "s" The symbol is in an uninitialized or zero-initialized data section for small objects.
          
          
          
          J Offline
          J Offline
          JonB
          wrote on 17 Feb 2022, 21:53 last edited by JonB
          #11

          @Kent-Dorfman
          The OP asks about .obj files from MSVC. You sure UNIX/GNU nm is available and works on these?

          K 1 Reply Last reply 17 Feb 2022, 23:42
          0
          • J JonB
            17 Feb 2022, 21:53

            @Kent-Dorfman
            The OP asks about .obj files from MSVC. You sure UNIX/GNU nm is available and works on these?

            K Offline
            K Offline
            Kent-Dorfman
            wrote on 17 Feb 2022, 23:42 last edited by
            #12

            @JonB if the object formt is COFF then it will work, even if OP has to build the utility themself. online info suggests that .obj format in windows is in fact COFF.

            J 1 Reply Last reply 18 Feb 2022, 09:45
            0
            • K Kent-Dorfman
              17 Feb 2022, 23:42

              @JonB if the object formt is COFF then it will work, even if OP has to build the utility themself. online info suggests that .obj format in windows is in fact COFF.

              J Offline
              J Offline
              JonB
              wrote on 18 Feb 2022, 09:45 last edited by
              #13

              @Kent-Dorfman
              I see, if you say so. Still not sure that OP would have a GNU nm utility available. FWIW, What COFF (windows .obj object file) viewers are available? for example states

              I am only aware of 2:

              dumpbin which is included with Visual Studio

              PEView from http://wjradburn.com/software/

              J 1 Reply Last reply 20 Feb 2022, 09:54
              0
              • K Offline
                K Offline
                Kent-Dorfman
                wrote on 18 Feb 2022, 18:52 last edited by Kent-Dorfman
                #14

                @JonB said in view content of .obj file generated by MSVC compiler ?:

                Still not sure that OP would have a GNU nm utility available.

                mingw provides the whole slew of gnu utilities as windows native executables. nm should be available, at which point the mingw exe can be used to process the windows native object file.

                With a caveat that most folks would probably overlook: OP wants to process C++ object files, in which case the symbol names will probably be name-mangled, unless they were declared as extern "C" {}

                J 1 Reply Last reply 18 Feb 2022, 19:20
                1
                • K Kent-Dorfman
                  18 Feb 2022, 18:52

                  @JonB said in view content of .obj file generated by MSVC compiler ?:

                  Still not sure that OP would have a GNU nm utility available.

                  mingw provides the whole slew of gnu utilities as windows native executables. nm should be available, at which point the mingw exe can be used to process the windows native object file.

                  With a caveat that most folks would probably overlook: OP wants to process C++ object files, in which case the symbol names will probably be name-mangled, unless they were declared as extern "C" {}

                  J Offline
                  J Offline
                  JonB
                  wrote on 18 Feb 2022, 19:20 last edited by JonB
                  #15

                  @Kent-Dorfman said in view content of .obj file generated by MSVC compiler ?:

                  mingw provides the whole slew of gnu utilities as windows native executables. nm should be available,

                  Ooohhh, sorry, right, that makes sense!

                  Though I thought MinGW did .o not .obj files, I thought that meant MSVC. But what do I know?! :)

                  1 Reply Last reply
                  0
                  • C Offline
                    C Offline
                    Chris Kawa
                    Lifetime Qt Champion
                    wrote on 18 Feb 2022, 19:44 last edited by
                    #16

                    You don't need any unix or otherwise external tools. MSVC installation already comes with the dumpbin utility that lets you see various information about the structure and contents of COFF files. It also undecorates C++ function names, so no problem there either.

                    V 1 Reply Last reply 20 Feb 2022, 08:57
                    3
                    • C Chris Kawa
                      18 Feb 2022, 19:44

                      You don't need any unix or otherwise external tools. MSVC installation already comes with the dumpbin utility that lets you see various information about the structure and contents of COFF files. It also undecorates C++ function names, so no problem there either.

                      V Offline
                      V Offline
                      Vinoth Rajendran4
                      wrote on 20 Feb 2022, 08:57 last edited by
                      #17

                      @Chris-Kawa : Thanks for the utility tool suggestion.

                      1 Reply Last reply
                      0
                      • K Kent-Dorfman
                        17 Feb 2022, 21:16
                        NM(1)                                                                                                      GNU Development Tools                                                                                                     NM(1)
                        
                        NAME
                               nm - list symbols from object files
                        
                        SYNOPSIS
                               nm [-A|-o|--print-file-name] [-a|--debug-syms]
                                  [-B|--format=bsd] [-C|--demangle[=style]]
                                  [-D|--dynamic] [-fformat|--format=format]
                                  [-g|--extern-only] [-h|--help]
                                  [-l|--line-numbers] [--inlines]
                                  [-n|-v|--numeric-sort]
                                  [-P|--portability] [-p|--no-sort]
                                  [-r|--reverse-sort] [-S|--print-size]
                                  [-s|--print-armap] [-t radix|--radix=radix]
                                  [-u|--undefined-only] [-V|--version]
                                  [-X 32_64] [--defined-only] [--no-demangle]
                                  [--plugin name]
                                  [--no-recurse-limit|--recurse-limit]]
                                  [--size-sort] [--special-syms]
                                  [--synthetic] [--with-symbol-versions] [--target=bfdname]
                                  [objfile...]
                        
                        DESCRIPTION
                               GNU nm lists the symbols from object files objfile....  If no object files are listed as arguments, nm assumes the file a.out.
                        
                               For each symbol, nm shows:
                        
                               ·   The symbol value, in the radix selected by options (see below), or hexadecimal by default.
                        
                               ·   The symbol type.  At least the following types are used; others are, as well, depending on the object file format.  If lowercase, the symbol is usually local; if uppercase, the symbol is global (external).  There are
                                   however a few lowercase symbols that are shown for special global symbols ("u", "v" and "w").
                        
                                   "A" The symbol's value is absolute, and will not be changed by further linking.
                        
                                   "B"
                                   "b" The symbol is in the BSS data section.  This section typically contains zero-initialized or uninitialized data, although the exact behavior is system dependent.
                        
                                   "C" The symbol is common.  Common symbols are uninitialized data.  When linking, multiple common symbols may appear with the same name.  If the symbol is defined anywhere, the common symbols are treated as undefined
                                       references.
                        
                                   "D"
                                   "d" The symbol is in the initialized data section.
                        
                                   "G"
                                   "g" The symbol is in an initialized data section for small objects.  Some object file formats permit more efficient access to small data objects, such as a global int variable as opposed to a large global array.
                        
                                   "i" For PE format files this indicates that the symbol is in a section specific to the implementation of DLLs.  For ELF format files this indicates that the symbol is an indirect function.  This is a GNU extension to the
                                       standard set of ELF symbol types.  It indicates a symbol which if referenced by a relocation does not evaluate to its address, but instead must be invoked at runtime.  The runtime execution will then return the value to
                                       be used in the relocation.
                        
                                   "I" The symbol is an indirect reference to another symbol.
                        
                                   "N" The symbol is a debugging symbol.
                        
                                   "p" The symbols is in a stack unwind section.
                        
                                   "R"
                                   "r" The symbol is in a read only data section.
                        
                                   "S"
                                   "s" The symbol is in an uninitialized or zero-initialized data section for small objects.
                        
                        
                        
                        V Offline
                        V Offline
                        Vinoth Rajendran4
                        wrote on 20 Feb 2022, 08:58 last edited by
                        #18

                        @Kent-Dorfman : Thanks for suggesting nm utility.

                        1 Reply Last reply
                        0
                        • J JonB
                          18 Feb 2022, 09:45

                          @Kent-Dorfman
                          I see, if you say so. Still not sure that OP would have a GNU nm utility available. FWIW, What COFF (windows .obj object file) viewers are available? for example states

                          I am only aware of 2:

                          dumpbin which is included with Visual Studio

                          PEView from http://wjradburn.com/software/

                          J Offline
                          J Offline
                          JonB
                          wrote on 20 Feb 2022, 09:54 last edited by JonB
                          #19

                          @JonB said in view content of .obj file generated by MSVC compiler ?:

                          (https://stackoverflow.com/questions/2262959/what-coff-windows-obj-object-file-viewers-are-available) for example states
                          I am only aware of 2:

                          dumpbin which is included with Visual Studio

                          PEView from http://wjradburn.com/software/

                          1 Reply Last reply
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                          20 Feb 2022, 08:57

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