问题
I am having trouble compiling a C library (gmp) for iOS 9 using the latest Xcode 7-beta clang. I am trying to produce bitcode to get all the warnings in Xcode to stop (and I would like to produce these libraries in bitcode). However, I can't even compile the library in the first place. ./configure fails, and after looking at the config.log, it seems ld is the problem as it is failing with "ld: library not found for -lSystem". Here is the command I have used to compile gmp in the past :
./configure CC=clang CPP="/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -E" CPPFLAGS="-isysroot /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/ -L /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/lib/ -miphoneos-version-min=7.0 -arch armv7 -target arm-apple-darwin
The
-L /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/lib/
flag I added is to see if that would help with ld finding the required libraries to link, but it fails with the same error whether I include that option or not. I have not include the option to compile into bitcode in the above command, as I I can't even get it to compile in the first place using the same command I used to use. I have noticed that when I add the gmp .a files to xcode under "link binary with libraries", that ld can't find the libraries. I must manually add the project to the ld search path in the project settings for ld to find the libraries. This wasn't necessary in Xcode 6, so is it just ld being buggy in the current beta, or is there anything I can do?
回答1:
Okay, here is what worked. Set your xcode development to use the new compilers using
sudo xcode-select -s /Applications/Xcode-beta.app
Then, I used this configure :
./configure CC=clang CPP="/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -E" CPPFLAGS="-isysroot /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/ -fembed-bitcode -miphoneos-version-min=7.0 -arch armv7 -target arm-apple-darwin" --host=aarch64-apple-darwin --disable-assembly --enable-static --disable-shared --disable-thread-safe --enable-cxx
The above works when compiling mpfr and mpc also.
来源：https://stackoverflow.com/questions/31279973/compiling-c-library-for-ios-9-from-command-line-xcode-7-beta-2