What is o file

Question

I m compiling own project  And it halted by this error      LINK  fatal error LNK1181  cannot open   input file    obj win release src lua bindings o     Compiling using Code  Blocks with VS 2005 2008 compiler under win7  There are also lot of another empty directories where   o files are missing   What do they do

User · Accepted Answer

A file ending in  o is an object file  The compiler creates an object file for each source file  before linking them together  into the final executable

User · Answer

You ve gotten some answers  and most of them are correct  but miss what  I think  is probably the point here   My guess is that you have a makefile you re trying to use to create an executable  In case you re not familiar with them  makefiles list dependencies between files  For a really simple case  it might have something like   myprogram exe  myprogram o       CC  -o myprogram exe myprogram o  myprogram o  myprogram cpp       CC  -c myprogram cpp   The first line says that myprogram exe depends on myprogram o  The second line tells how to create myprogram exe from myprogram o  The third and fourth lines say myprogram o depends on myprogram cpp  and how to create myprogram o from myprogram cpp  respectively   My guess is that in your case  you have a makefile like the one above that was created for gcc  The problem you re running into is that you re using it with MS VC instead of gcc  As it happens  MS VC uses   obj  as the extension for its object files instead of   o    That means when make  or its equivalent built into the IDE in your case  tries to build the program  it looks at those lines to try to figure out how to build myprogram exe  To do that  it sees that it needs to build myprogram o  so it looks for the rule that tells it how to build myprogram o  That says it should compile the  cpp file  so it does that   Then things break down -- the VC   compiler produces myprogram obj instead of myprogram o as the object file  so when it tries to go to the next step to produce myprogram exe from myprogram o  it finds that its attempt at creating myprogram o simply failed  It did what the rule said to do  but that didn t produce myprogram o as promised  It doesn t know what to do  so it quits and give you an error message   The cure for that specific problem is probably pretty simple  edit the make file so all the object files have an extension of  obj instead of  o  There s room for a lot of question whether that will fix everything though -- that may be all you need  or it may simply lead to other  probably more difficult  problems

User · Answer

Ink-Jet is right   More specifically  an  o   obj  -- or object file is a single source file compiled in to machine code  I m not sure if the  machine code  is the same or similar to an executable machine code   Ultimately  it s an intermediate between an executable program and plain-text source file   The linker uses the o files to assemble the file executable   Wikipedia may have more detailed information  I m not sure how much info you d like or need

User · Answer

A  o object file file  also  obj on Windows  contains compiled object code  that is  machine code produced by your C or C   compiler   together with the names of the functions and other objects the file contains  Object files are processed by the linker to produce the final executable  If your build process has not produced these files  there is probably something wrong with your makefile project files

User · Answer

It is important to note that object files are assembled to binary code in a format that is relocatable  This is a form which allows the assembled code to be loaded anywhere into memory for use with other programs by a linker    Instructions that refer to labels will not yet have an address assigned for these labels in the  o file    These labels will be written as  0  and the assembler creates a relocation record for these unknown addresses  When the file is linked and output to an executable the unknown addresses are resolved and the program can be executed   You can use the nm tool on an object file to list the symbols defined in a  o file

[c++] What is *.o file?

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