I need to include a binary program in my project. I use objcopy to create an object file from a binary file. The object file can be linked in my program. objcopy creates appropriate symbols to access the binary data.
Example
objcopy -I binary -O elf32-littlearm --binary-architecture arm D:\Src\data.jpg data.o
The generated symbols are:
_binary_D__Src_data_jpg_end
_binary_D__Src_data_jpg_size
_binary_D__Src_data_jpg_start
The problem is that the symbols include the path to the binary file D__Src_. This may help when binary files are included from different location. But it bothers me that the symbols changes when I get the file from a different location. Since this shall run on several build stations, the path can't be stripped with the --redefine-sym option.
How do I get rid of the path in the symbol name?
I solved this problem by using this switch in objcopy:
--prefix-sections=abc
This gives a way to uniquely identify the data in your binary object file (ex. binary.o)
In your linker script you can then define your own labels around where you include the binary.o. Since you are no longer referencing anything in binary.o the binary will be thrown out by the linker if you use -gc-sections switch. The section in binary.o will now be abc.data. Use KEEP in your linker script to tell the linker not to throw out binary.o. Your linker script will contain the following:
__binary_start__ = .;
KEEP(*(abc.data))
binary.o
*(abc.data)
. = ALIGN(4);
__binary_end__ = .;
The switch --localize-symbols works for me.
Related
I am using Doxygen for documentation of my project. I have a compile_commands.json file describing the source code of my project inside the directory C:\dev\project_dir. I set the following variables:
CLANG_ASSISTED_PARSING = YES
CLANG_DATABASE_PATH = C:\dev\project_dir
So how does this work? Do I also have to set the variables INPUT and INCLUDE_PATH? It seems that all the files and the instructions to compile them, including where to get header files from, are written in the compilation database.
And if I do have to set the variables INPUT and INCLUDE_PATH also, what should I set them to? The compilation database lists the source and header files of the project, which are scattered among multiple different directories. How should I proceed in this situation.
I found the answer.
So I set the following variables in the Doxyfile.
CLANG_ASSISTED_PARSING = YES
CLANG_DATABASE_PATH = C:\dev\project_dir
And I set the following variables as blank:
INPUT =
INCLUDE_PATH =
INPUT specifies the paths to source code *.c *.cpp files and/or directories to be processed. INCLUDE_PATH specifies the paths to header code *.h *.hpp files and/or directories to be processed.
The CLANG_ASSISTED_PARSING = YES enables using clang compiler as the parser instead of the default doxygen parser. So if INPUT and INCLUDE_PATH are not set, then it gets the source code files and header code files from the compilation database itself. The CLANG_DATABASE_PATH specifies the directory in which the compilation database is stored. It grabs the file named compile_commands.json by default from that directory, implying that the name of the compilation database is fixed. If you name your compilation database JSON file anything else other than compile_commands.json doxygen won't be able to find it.
So if a clang compilation database JSON file is used all the *.c *.cpp files that are being compiled are placed in the INPUT. And all the header code files are placed in the INCLUDE_PATH. The clang used by doxygen parses the JSON, and every time it encounters a -I compiler flag it recognizes that file as a header file, adding it to the INCLUDE_PATH. This means that setting INPUT and INCLUDE_PATH are not mandatory. So if the compilation database is properly formatted, and all the header files are explicitly marked with the -I, only setting the CLANG_DATABASE_PATH is sufficient.
But there is a certain situation when the INCLUDE_PATH also needs to be set explicitly. For example if you have a source code file, which includes a header file, which includes another header file inside of it.
first.h
int one(int);
second.h
#include "first.h"
int two(int);
code.cpp
#include "second.h"
int main(void) {}
And the command in the compilation database is such:
clang -I path/to/second.h -c code.cpp
So in this case doxygen would read that file, and it would internally set the following variables as such:
INPUT = code.cpp
INCLUDE_PATH = path/to/second.h
This means that although doxygen will index second.h, it will miss first.h since that header file isn't explicitly provided in the -I compilation database. That would be an error. So we need to list it explicitly in the doxyfile, an an additional include path.
INPUT =
INCLUDE_PATH = path\to\first.h
CLANG_ASSISTED_PARSING = YES
CLANG_DATABASE_PATH = C:\dev\project_dir
When I build java object class in a project, build file will be created with .class extension and human unreadable; What about swift build files?
example:
car.java --> build --> car.class
what would be after build?
car.swift --> build --> ?
The compilation process is a bit different with Swift to Java, so there isn't necessarily a direct equivalent.
As the build proceeds though each Swift file will get compiled in to an 'Object' file, ending in a .o extension. Then once they're all built they get linked together to form the binary. If you unpick an iOS app's IPA file, you won't see the individual .o files like how you can see the .class files inside a Java jar file.
One thing I know is that Swift uses LLVM just like Objective-C.
So in Java, we have this (source: W3schools).
And here, for Swift (source: Swift.org)
I hope this helps!
Mach-O format
[LLVM]
In iOS world every sources file - .m, .h, .swift are compiled into executable byte code that is understandable by CPU. These files are also called Mach object(.o) - ABI Mach-O[About] file which contains nexts grouped bytes with a meta-information
Mach-O header - general information like cpu type(CPU_TYPE)
Load Commands - table of contents
Raw segment data - code
__LLVM - bitcode[About]
This groups are repeated for every architecture(Universal library)[About]
`*.swift` -> `*.o` (Mach-O object file)
For example if you created a static library - myLibrary.a. You can use nm[About] command to display name list (symbol table).
nm path/myLibrary.a
As a result you will see a list of *.o files with methods, variables names etc.
To investigate Mach-O file you can use otool[About]
[Mach-O Type]
[Xcode build process]
I am working in Linux and I have a library written in Fortran 90 (written by 3rd party), that is reading from a file in the current working directory. I would like to be able to call the resulting library from other folders, hence I need to read the path where the library is installed. How can I know the path to the compiled library within the Fortran code?
I need to store in a variable the path within the code.
For who knows python, I want to achieve the same as
import os
os.path.dirname(os.path.abspath(__file__))
but in f90 (see Get location of the .py source file)
Using the suggestions in the comment I have done the following:
export DATAPATH=`pwd`
make
in the Makefile
ifort -O3 -fpic -fpp -DDATAPATH -c mysource.f90
in mysource.f90
subroutine mysub
character(len=100)::dpath
#ifdef DATAPATH
dpath=DATAPATH
#endif
open(10,file=trim(dpath)//'initialise.dat')
....
....
the problem is that at compile time I get
mysource.f90(42): error #6054: A CHARACTER data type is required in this context. [1]
dpath=1
----------^
compilation aborted for mysource.f90 (code 1)
If you wish you can fix the path at compile time. Something like
gfortran -cpp mylib.f90 -DPREFIX=\"/usr/local/\"
open(newunit=u,file=PREFIX//'mylib/initialise.dat')
You must than make sure the library is indeed installed in that place PREFIX/mylib/
You can create an environment variable containing the path of your data. This variable can be set by hand, in your .bashrc or .bash_profile or in the system /etc/profile.d/ or /etc/bash.bashrc, there are manyways and they depend if the library is just for one user or for all users of some large computer.
For example
export MYLIB_PATH='/usr/local/mylib'
Then you can read the variable in Fortran as
CALL get_environment_variable("MYLIB_PATH", mylib_path, status=stat)
and the path is now in variable mylib_path. You can check the success by checking if stat==0.
This is not the only possible approach. You can also have a configuration file for your library in your home directory:
mkdir $HOME/.config/mylib/
echo "/usr/local/mylib" > $HOME/.config/mylib/path
and then you can try to read the path from this file if the environment variable was not set
if (stat/=0) then
CALL get_environment_variable("HOME", home_dir)
open(newunit=path_unit, file=home_dir//'/.config/mylib/path',status='old',action='read',iostat=stat)
if (stat/=0) complain
read(path_unit,'(a)',iostat=stat) mylib_path
if (stat/=0) complain
end if
So when you compiled with -DDATAPATH you have not passed the variable DATAPATH into your code only declared a symbol called DATAPATH as being true, so ifort will substitute DATAPATH as 1. What you need to do is pass it as a value:
-DDATAPATH="$(DATAPATH)"
For the compilation to work.
Using xcode 6 and including files with names like Some$$Class.h and Some$$Class.m leads to problems. Xcode shows to error:
clang: error: no such file or directory: '/Users/test/Some$ClassX.m'
clang: error: no input files
How can I force Xcode to handle files with $$in its name correctly?
There is a very! dirty hack.
If you look to the error message, you can see that the build process of Xcode replaces the $$ of Some$$Class.m with a single $. (Obviously there is no problem with Some$$Class.h) It is an escape sequence.
Some$$Class.m -> Some$Class.m
Therefore you can use Some$$$$Class.m to get Some$$Class.m.
Simply add an (empty) File with the name Some$$$$Class.m to your project to show Xcode that it exists. You have to do this once.
Generate your Some$$Class.m as you did as many times as you want.
When building Xcode will believe that it compiles and links Some$$$$Class.m, but in fact compiles and builds Some$$Class.m.
But you should really, really avoid these names. If the files are generated automatically it should be possible to rename them automatically.
This error happens when I try to import the file "VARendererViewController.h" from the file "VAMenuScreenViewController"
duplicate symbol _gestureMinimumTranslation in:
/Users/Sam/Library/Developer/Xcode/DerivedData/Virtual_Human_Avatar-fwgdkxpnkzapxrdzkggtmbnfhjwb/Build/Intermediates/Virtual Human Avatar.build/Debug-iphonesimulator/Virtual Human Avatar.build/Objects-normal/i386/VARendererViewController.o
/Users/Sam/Library/Developer/Xcode/DerivedData/Virtual_Human_Avatar-fwgdkxpnkzapxrdzkggtmbnfhjwb/Build/Intermediates/Virtual Human Avatar.build/Debug-iphonesimulator/Virtual Human Avatar.build/Objects-normal/i386/VAMenuScreenViewController.o
ld: 1 duplicate symbol for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Could anyone provide me with some
You have two compilation units -- two source files -- that are defining the same symbol.
This may be because you defined the symbol in two separate .m files (or other compilation unit; .c, .mm, etc...) or because you defined the symbol in a header file and imported it into those two files. Alternatively, if you shove a variable declaration into a header file without the extern, then it'll cause a symbol by that name to be created in every .m file it is imported into.
Assuming gestureMinimumTranslation is a variable, then if you really want a global variable, it should be defined in only one .m file as follows:
int gestureMinimumTranslation;
Then, in the corresponding header:
extern int gestureMinimumTranslation;
And the other .m file should import the above header.
The linker is trying to join a set of objects with a common symbol. This often happens when the Compile Sources Build Phase has duplicate entries or a header file. Try removing these.