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.
Related
:0: error: filename "SurveyViewController.swift" used twice: '/Users/raeessamman/Downloads/fwdsurver/SurveyViewController.swift' and '/Users/raeessamman/Desktop/IOS Development projects/SammanMRA-cobsccomp191p-036/NIBM COVID19/NIBM COVID19/Controller/SurveyViewController.swift'
:0: note: filenames are used to distinguish private declarations with the same name
Command CompileSwiftSources failed with a nonzero exit code
search with this name "SurveyViewController" in your project
you will find that you declare it twice. you must change or delete one of them.
if you didn't find it you must search in "project.pbxproj" file and you will find two paths with the same name.
to open the "project.pbxproj" file you should go to "YourApp.xcodeproj" then you double click in it, menu will open select "show package contents" then you will find 2 files one of them is "project.pbxproj".
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]
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.
Sorry for asking this newbie question but I can't get off this s***t...
In the same directory I have 4 files : ctacs.ini; ct_api.h; libctacs.a and main.cpp.
My cpp file contains #include "ct_api.h" and when I try to compile with :
g++ -lctacs main.cpp -o main
I got undefined references to the functions which are defined in my library -__-
Could you please tell what did I wrong ? I search on the internet but the option -lctacs seems to be the right way to proceed...
Thank you very much
Some compilers and linkers resolve references to functions by searching the object files/sources files/libraries left-to-right on the command line. This means that files that call externally-defined functions should appear before the object files/libraries/source files that contain their definitions.
You happen to have a linker that does indeed depend on this ordering. You need to put the library after main.cpp so that the function definitions can be found:
g++ main.cpp -lctacs -o main
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.