Linking issue on MacOS Catalina (using XCode)

[Samyukta Yagati]

I installed Crypto++ from source as follows:

1. git clone https://github.com/weidai11/cryptopp.git
2. cd cryptopp
3. Uncommented the CXX flag line in GNUmakefile that adds "-stdlib=libc++" because I am using XCode. 
4. make -j 8 (8 = value of $(nproc) on my machine if it were linux)
5. sudo make install

The make and install complete without errors. I confirmed that /usr/local/lib contains libcryptopp.a.

When I try to use libcryptopp in a project (in a different directory from the cryptopp install), clang (Apple Clang 12.0.0) can't find it. I get the following error message:

+ LD     lib/crypto_bench
ld: library not found for -l:libcryptopp.a
clang: error: linker command failed with exit code 1 (use -v to see invocation)

This is the output of gcc --version (gcc is linked to clang but not directly used):

Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/4.2.1

Apple clang version 12.0.0 (clang-1200.0.32.29)

Target: x86_64-apple-darwin19.6.0

Thread model: posix

InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

I also tried updating my PATH variable in bash_profile with the location of libcryptopp as follows, then source'd bash_profile again:

export PATH="/usr/local/lib:$PATH"

However, this resulted in the same error as before when I tried to compile the project. I've spent several hours googling and haven't been able to find a fix, and I'm wary of manually symlinking the file because it can break other installs on my laptop. Any help with fixing this issue would be much appreciated.

[Jeffrey Walton]

On Wed, Sep 15, 2021 at 6:39 PM Samyukta Yagati <sa...@berkeley.edu> wrote:
>
> I installed Crypto++ from source as follows:
>
> git clone https://github.com/weidai11/cryptopp.git
> cd cryptopp
> Uncommented the CXX flag line in GNUmakefile that adds "-stdlib=libc++" because I am using XCode.
> make -j 8 (8 = value of $(nproc) on my machine if it were linux)
> sudo make install
>
> The make and install complete without errors. I confirmed that /usr/local/lib contains libcryptopp.a.
>
> When I try to use libcryptopp in a project (in a different directory from the cryptopp install), clang (Apple Clang 12.0.0) can't find it. I get the following error message:
>
> + LD lib/crypto_bench
> ld: library not found for -l:libcryptopp.a
> clang: error: linker command failed with exit code 1 (use -v to see invocation)
>

> ...

>
> I also tried updating my PATH variable in bash_profile with the location of libcryptopp as follows, then source'd bash_profile again:
>
> export PATH="/usr/local/lib:$PATH"
>
> However, this resulted in the same error as before when I tried to compile the project. I've spent several hours googling and haven't been able to find a fix, and I'm wary of manually symlinking the file because it can break other installs on my laptop. Any help with fixing this issue would be much appreciated.

When linking, use -L to provide a path to the linker. That is, you
invoke ld directly. If you are passing the linker option through the
compiler driver, then use -Wl,-L -Wl,<path>

So you would probably use something like:

clang++ -g2 -O3 -I /usr/local/include test.cxx -Wl,-L
-Wl,/usr/local/lib -o test.exe

You would have to do the same on, say, CentOS, Fedora and Red Hat. Red
Hat does not put /usr/local on-path for the build tools.

Jeff

[Samyukta Yagati]

I'm new to using clang, so to clarify: in my case, I should try "clang++ -g2 -O3 -I /usr/local/include cryptopp -Wl,-L" (where cryptopp is a subdirectory of include)? Also, is "-Wl,/usr/local/lib -o test.exe" intended to be shorthand for "clang++ -g2 -O3 -Wl,/usr/local/lib -o test.exe"? (and, relatedly, what output should I expect in test.exe?)

[Samyukta Yagati]

As a follow up: I tried running 

>> clang++ -g2 -O3 -l /usr/local/include /usr/local/lib/libcryptopp.a -WI,-L

And got the error:

ld: library not found for -l/usr/local/include

clang: error: linker command failed with exit code 1 (use -v to see invocation)

It seems like the intention of this command was to ask clang to link to the include path to crypto++ but clang doesn't have the include path on in its build tools? Further suggestions or clarifications would be great, I tried googling again and couldn't find anything.

[Jeffrey Walton]

On Thu, Sep 16, 2021 at 6:22 PM Samyukta Yagati <sa...@berkeley.edu> wrote:
>
> As a follow up: I tried running
>
> >> clang++ -g2 -O3 -l /usr/local/include /usr/local/lib/libcryptopp.a -WI,-L
>
> And got the error:
> ld: library not found for -l/usr/local/include
> clang: error: linker command failed with exit code 1 (use -v to see invocation)

That's an "I" as in "include", bot a lowercase "L".

Use this command:

clang++ -g2 -O3 -I /usr/local/include test.cxx

/usr/local/lib/libcryptopp.a -o test.exe

An archive like libcryptopp.a is just a collection of object files. It
is equivalent to saying:

clang++ -g2 -O3 -I /usr/local/include test.cxx

/usr/local/lib/cryptlib.o /usr/local/lib/cpu.o
/usr/local/lib/integer.o ... -o test.exe

A share object like libcryptopp.dylib or libcryptopp.so is the same
collection of object files in an executable format that can be loaded
at runtime.

Jeff

[Samyukta Yagati]

I think I'm still misunderstanding the intention of the command. 

On Thursday, September 16, 2021 at 3:56:20 PM UTC-7 Jeffrey Walton wrote:

That's an "I" as in "include", bot a lowercase "L".

Use this command:

clang++ -g2 -O3 -I /usr/local/include test.cxx
/usr/local/lib/libcryptopp.a -o test.exe

For the above command (I'm reading it as a single line, so all part of one command), is the test.cxx file something that's generated by the cryptopp install process? If so, which directory should I be running this from? (I don't see a test.cxx in the cryptopp directory and searching online suggests this is related to the google testing framework for C++).

 

If I run the following (without the test.cxx file as input, which probably doesn't make sense but again I couldn't tell what function it's serving):

>> clang++ -g2 -O3 -I /usr/local/include /usr/local/lib/libcryptopp.a -o test.exe

I get this error:

Undefined symbols for architecture x86_64:

  "_main", referenced from:

     implicit entry/start for main executable

ld: symbol(s) not found for architecture x86_64

Thank you for your help so far, I really appreciate it.

[Uri Blumenthal]

Say, you have a file that includes Crypto++ headers and needs linking with Crypto++ library. And Crypto++ is installed into /usr/local.

Then, the following would be sufficient:

clang++ -o my_binary -I/usr/local/include my_source.cpp -L /usr/local/lib -lcryptopp -lm

(I'm not sure if "-lm" is still necessary)


> On Sep 16, 2021, at 19:28, Samyukta Yagati <sa...@berkeley.edu> wrote:
>

[Samyukta Yagati]

Ah I see -- I'm using make with a custom makefile to build the source files in my project, is there a way to translate this to flags in the makefile?

[Samyukta Yagati]

(I currently have -l:libcryptopp.a in my LDFLAGS)

[Uri Blumenthal]

Sorry, I've no idea what your makefile looks like, or how to convey the working flags to it. 

On Sep 17, 2021, at 16:39, Samyukta Yagati <sa...@berkeley.edu> wrote:

(I currently have -l:libcryptopp.a in my LDFLAGS)

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[Samyukta Yagati]

Thanks for your help! Resolved, the issue was in my Makefile flags.