I'm writing C program in Xcode, and I got this problem:
ld: 1 duplicate symbol for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Any idea to solve it?
Note: I've just update my OS to Mountain Lion yesterday.
A common error is to define a symbol in a header when you wanted to declare it:
When you for instance declare a global variable and forget the extern or you define an inline function and forget the inline. In these cases the compiler emits the symbol in each compile unit that includes this header and you end up with multiple definitions of a symbol.
Anyway you should just look for the symbol in question.
Related
This question already has answers here:
Getting a "multiple definition of 'X' first defined here" error in C, although I only defined X once
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Multiple definitions errors showed up in project history in 2020. Now no commit before that point can be built without adding "extern"
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Closed last month.
When trying to compile and link two c modules with GCC, both containing a global variable with the same name, I get an error of multiple definitions.
Despite the fact that both are so-called weak symbols.
A code example:
I've tried to compile and link the 2 following c modules:
// b1.c
int x;
int main() {}
// b2.c
int x;
Now, supposedly, the var x in both files, should be a weak symbol.
So when linking, both should reference the same value.
But, for some reason, I get the following error:
$ gcc b1.c b2.c
/usr/bin/ld: /tmp/ccCP4DM3.o:(.bss+0x0): multiple definition of `x`; /tmp/ccN4Bd4O.o:(.bss+0x0): first defined here
collect2: error: ld returned 1 exit status
$ gcc --version
gcc 11.3.0
$ ld --version
GNU ld 2.38
So, did something change? Because according to the "Computer Systems
A Programmer’s Perspective" section 7.6, it should compile and link just fine using gcc without any special flags.
I am a beginner in both linux and openwrt. Sorry if this is a stupid question.
I am following this tutorial : https://downloads.openwrt.org/docs/eclipse.pdf
Chip : MT7620
Toolchain Prefix : mipsel-openwrt-linux-
Toolchain Path : /ligo/openwrt/staging_dir/toolchain-mipsel_24kec+dsp_gcc-5.3.0_musl-1.1.14
Code:
#include <stdio.h>
void main()
{
printf("Hello World");
}
Error:
**** Build of configuration Debug for project hello ****
make all
Building target: hello
Invoking: Cross GCC Linker
mipsel-openwrt-linux-gcc -L/ligo/openwrt/staging_dir/toolchain-mipsel_24kec+dsp_gcc-5.3.0_musl-1.1.14/lib -o"hello" ./main.o
mipsel-openwrt-linux-gcc: warning: environment variable 'STAGING_DIR' not defined
mipsel-openwrt-linux-gcc: warning: environment variable 'STAGING_DIR' not defined
/ligo/openwrt/staging_dir/toolchain-mipsel_24kec+dsp_gcc-5.3.0_musl-1.1.14/lib/gcc/mipsel-openwrt-linux-musl/5.3.0/../../../../mipsel-openwrt-linux-musl/lib/crt1.o: In function `_start_c':
/ligo/openwrt/build_dir/toolchain-mipsel_24kec+dsp_gcc-5.3.0_musl-1.1.14/musl-1.1.14/crt/crt1.c:17: undefined reference to `main'
/ligo/openwrt/build_dir/toolchain-mipsel_24kec+dsp_gcc-5.3.0_musl-1.1.14/musl-1.1.14/crt/crt1.c:17: undefined reference to `main'
collect2: error: ld returned 1 exit status
make: *** [hello] Error 1
add the following 2 lines at the end of bashrc
export PATH=$PATH:~/openwrt/staging_dir/toolchain-mipsel_24kec+dsp_gcc-4.8-linaro_uClibc-0.9.33.2/bin
export STAGING_DIR=~/openwrt/staging_dir
source ~/.bashrc
To open/create the bashrc you can execute
sudo gedit ~/.bashrc
Well I feel stupid when I have to figure this problem which happens too often.
I get the above error when I forget to save the file that contains main() it gives this error since the file is empty until you save it.
These instructions tell how to automatically save all the modified files when you kick off a build Save before build Keep this set and you won't see this again.
If you don't have the path to the toolchain set in eclipse, it never even finds a compiler, assembler or linker so it can not produce the error given. The warnings about STAGING_DIR are harmless in this case.
I know not many people have telepathic powers here, but I will try to give as much info as I can so someone can help me debug what I think is a linker error in some program I'm trying to compile.
So, the program is cilkprof (see here, warning: tgz file). Within it is a Makefile for which I only changed the var CXX = icpc to CXX = g++. All else is equal.
/usr/bin/ld: ../../3rdparty/pintool/intel64/lib/libpin.a(util_host_ia32e.os):
relocation R_X86_64_PC32 against symbol `DoXsave' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value
collect2: error: ld returned 1 exit status
make: *** [linux64/cilkprof.so] Error 1
I know I should be understanding that libpin.a should be recompiled with -fPIC, but the pin version I have is already compiled. Any idea what I may be doing wrong? Please ask if something is not clear. Thanks.
It seems to me that the Makefile is trying to build a shared library and link it to a static non-PIC library, which is AFAIK, something you can't do. So if you can not recompile the libray with -fPIC then the only solution I see is to modify the Makefile and build a static library instead.
I'm having a problem using min() and max() function in my C project. I've imported math.h, but when I compile the file I keep getting the following error (a similar error is displayed even using gcc instead of llvm):
Undefined symbols for architecture x86_64:
"_min", referenced from:
_main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
I think the problem is that there isn't a 64 bit library of math.h... or the compiler can't find it. I'm using Mac OS X 10.7. How may I fix this problem?
Even though I can see "min" defined in libSystem.dylib, I don't think there's an exported header for that. And I can't figure out where "_min" is coming in from, in terms of the include files.
Normally "min" is referred to with a macro or with your own function. Check out this very related question somebody else asked a while back.
If you look in math.h, there are some "min" type functions in there but they are for floats and doubles. If you are just working with integers or custom types, roll your own function.
I just started learning C, and wrote my hello world program:
#include <stdio.h>
main()
{
printf("Hello World");
return 0;
}
When I run the code, I get a really long error:
Apple Mach-O Linker (id) Error
Ld /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug/CProj normal x86_64
cd /Users/Solomon/Desktop/C/CProj
setenv MACOSX_DEPLOYMENT_TARGET 10.7
/Developer/usr/bin/clang -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.7.sdk -L/Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug -F/Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug -filelist /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Intermediates/CProj.build/Debug/CProj.build/Objects-normal/x86_64/CProj.LinkFileList -mmacosx-version-min=10.7 -o /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Products/Debug/CProj
ld: duplicate symbol _main in /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Intermediates/CProj.build/Debug/CProj.build/Objects-normal/x86_64/helloworld.o and /Users/Solomon/Library/Developer/Xcode/DerivedData/CProj-cwosspupvengheeaapmkrhxbxjvk/Build/Intermediates/CProj.build/Debug/CProj.build/Objects-normal/x86_64/main.o for architecture x86_64
Command /Developer/usr/bin/clang failed with exit code 1
I am running xCode
Should I reinstall DevTools?
If you read the error messages (specifically the line starting ld: duplicate symbol _main in ...), you'll notice that it's complaining about two main functions, one in:
......blah blah blah/helloworld.o
and the other in:
......yada yada yada/main.o
That means your project is screwed up somehow. Either you have two separate source files containing main or Xcode is supplying one automagically.
You just need to fix that.
Here's how to interpret that message:
Apple Mach-O Linker (id) Error
An error occurred
Ld /Users/ …
cd …
setenv …
/Developer/…
This is the command that Xcode executed to perform the linking step. You can almost always ignore it and skip past the next blank line.
ld: duplicate symbol _main in /Users/…/helloworld.o and /Users/…/main.o for architecture x86_64
This is the actual error message. It tells you that you have duplicate _main symbols, one in the file helloworld.o and one in main.o. This means you have to functions which are both called main, which isn't allowed. One of them is in helloworld.c and the other is in main.c. If you delete one of these functions or files, the error will go away.
Command /Developer/usr/bin/clang failed with exit code 1
This tells you the exit code of the command Xcode performed. It is less helpful than the error message, and I have never seen anything other than 1 for linking errors.
I meet this problem as well. In "Target Membership", just tick the file you want to run. Untick this in other files you don't want to run. Then try again.
It is also important to remember that you could have received this error message if you had a #include "...filename..." that created a duplicate copy of your function calls. However, in your case, that is not likely.
remember that #include essentially just copies and pastes a copy of your code where the #include takes place.