How to cross-compile clang/llvm 3.7.0 for iOS8.x o

EDIT, 2015-10-24. This finally worked :

../configure --prefix=/usr/local/lvm-cross/llvm-ios --with-default-sysroot=/usr/local/iPhoneOS8.4.sdk --host=arm-apple-darwin11 --enable-optimized --disable-assertions --disable-libedit

with

clang -isysroot /usr/local/iPhoneOS8.4.sdk/ -target arm64-apple-darwin11 testcpp.cpp -o testcpp

where testcpp.cpp contains :

int main()
{
    return 0;
}

Now if I modfified the source code simply as follows :

#include <iostream> // I am not even calling << operator in code, just including
int main()
{
    return 0;
}

the following problem appears :

Undefined symbols for architecture arm64:
  "std::ios_base::Init::Init()", referenced from:
      ___cxx_global_var_init in testcpp-0b9c00.o
  "std::ios_base::Init::~Init()", referenced from:
      ___cxx_global_var_init in testcpp-0b9c00.o
ld: symbol(s) not found for architecture arm64

Verbosity with -v gives this :

XXXXs-iPad:~/Documents/CODING/MY/TESTS/CPP mobile$ clang -v -isysroot /usr/local/iPhoneOS8.4.sdk -target arm64-apple-darwin11 testcpp.cpp -o testcpp
clang version 3.7.0 (tags/RELEASE_370/final)
Target: arm64-apple-darwin11
Thread model: posix
 "/usr/local/llvm-ios/bin/clang" -cc1 -triple arm64-apple-ios5.0.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -Werror=implicit-function-declaration -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name testcpp.cpp -mrelocation-model pic -pic-level 2 -mthread-model posix -mdisable-fp-elim -masm-verbose -target-cpu generic -target-feature +neon -target-abi darwinpcs -target-linker-version 253.3.3 -v -dwarf-column-info -resource-dir /usr/local/llvm-ios/bin/../lib/clang/3.7.0 -isysroot /usr/local/iPhoneOS8.4.sdk -fdeprecated-macro -fdebug-compilation-dir /var/mobile/Documents/CODING/MY/TESTS/CPP -ferror-limit 19 -fmessage-length 132 -stack-protector 1 -mstackrealign -fallow-half-arguments-and-returns -fblocks -fobjc-runtime=ios-5.0.0 -fencode-extended-block-signature -fcxx-exceptions -fexceptions -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -o /var/tmp/testcpp-b164d6.o -x c++ testcpp.cpp
clang -cc1 version 3.7.0 based upon LLVM 3.7.0 default target arm-apple-darwin14.0.0
ignoring nonexistent directory "/usr/local/iPhoneOS8.4.sdk/usr/include/c++/4.2.1/arm64-apple-darwin10/"
ignoring nonexistent directory "/usr/local/iPhoneOS8.4.sdk/usr/local/include"
ignoring nonexistent directory "/usr/local/iPhoneOS8.4.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/iPhoneOS8.4.sdk/usr/include/c++/4.2.1
 /usr/local/iPhoneOS8.4.sdk/usr/include/c++/4.2.1/backward
 /usr/local/llvm-ios/bin/../lib/clang/3.7.0/include
 /usr/local/iPhoneOS8.4.sdk/usr/include
 /usr/local/iPhoneOS8.4.sdk/System/Library/Frameworks (framework directory)
End of search list.
 "/usr/bin/ld" -demangle -dynamic -arch arm64 -iphoneos_version_min 5.0.0 -syslibroot /usr/local/iPhoneOS8.4.sdk -o testcpp /var/tmp/testcpp-b164d6.o -lSystem
Undefined symbols for architecture arm64:
  "std::ios_base::Init::Init()", referenced from:
      ___cxx_global_var_init in testcpp-b164d6.o
  "std::ios_base::Init::~Init()", referenced from:
      ___cxx_global_var_init in testcpp-b164d6.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

EDIT, 2015-10-21. This time I configured with :

../configure --prefix=/usr/local/lvm-cross/llvm-ios --target=arm-apple-darwin11 --host=arm-apple-darwin11 --with-default-sysroot=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.4.sdk --enable-optimized --disable-assertions --disable-libedit

Trying to compile with clang++ -v testcpp.cpp -o testcpp again throws then the following error :

"ld" -demangle -dynamic -arch armv4t -macosx_version_min 10.10.0 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.4.sdk -o testcpp /var/tmp/testcpp-bb42e7.o -lc++ -lSystem
arm-apple-darwin11-clang++: error: unable to execute command: Executable "ld" doesn't exist!
arm-apple-darwin11-clang++: error: linker command failed with exit code 1 (use -v to see invocation)

I still have this -macosx_version_min 10.10.0 stuff : bad moon rising ; worrying. Installing org.coolstar.cctools and org.coolstar.ld64 via Cydia and recompiling gave :

"/usr/bin/ld" -demangle -dynamic -arch armv4t -macosx_version_min 10.10.0 -syslibroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.4.sdk -o testcpp /var/tmp/testcpp-5ae1b0.o -lc++ -lSystem
ld: library not found for -lc++
arm-apple-darwin11-clang++: error: linker command failed with exit code 1 (use -v to see invocation)

still the ld: library not found for -lc++ error. Note that adding -isysroot=/path/to/the/iphonesdk/that/i/copied/from/my/mac/to/my/idevice to the compilation did not change a single thing to what I have stated above.

EDIT, 2015-10-18, IV. Installing the package "Darwin CC Tools" from the BigBoss source via cydia furnishes the ld command line executable. Trying to compile with clang++ -v testcpp.cpp -o testcpp again throws then the following error :

"/usr/bin/ld" -demangle -dynamic -arch armv4t -macosx_version_min 10.10.0 -o testcpp /var/tmp/testcpp-ddd8d4.o -lc++ -lSystem
ld: library not found for -lc++
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

I guess that it means that ld can't find the place where the c++ standard library files are. How to deal with this ?

EDIT, 2015-10-18, III. Retrospectively I think there must be an issue with the configure step. On the iPad when I try to compile with clang++ -v testcpp.cpp -o testcpp it produce a natural error saying that ld is missing, but it shows something strange : "ld" -demangle -dynamic -arch armv4t -macosx_version_min 10.10.0 -o testcpp /var/tmp/testcpp-a74741.o -lc++ -lSystem What does this -macosx_version_min 10.10.0 do here ? It is as if the compiler was looking for the (mac os) linker of the plateform it was cross-build with instead of the iOS one...

EDIT, 2015-10-18, II. Actually I copied the whole iOS8.4 sdk to the iPad, and I will -isysroot to it during compilation. I tried to compile the simplest c++ code

int main()
{
    return 0;
}

in testcpp.cpp with clang++ -v testcpp.cpp -o testcpp which led to a natural linking error (as I don't have a linker yet !) :

clang++: error: unable to execute command: Executable "ld" doesn't exist!
clang++: error: linker command failed with exit code 1 (use -v to see invocation)

As I don't know which strategy to opt for, I created a question :

Almost naked iOS8.4 --> how to get a linker?

EDIT, 2015-10-18, I. Passing --disable-libedit at the configure step allowed me to elude the 'histedit.h' file not found error. Had then again a crt_externs.h file not found error in ProgramTest.cpp that I get rid of by commenting the #include, which led to this error

/Users/XXXX/Documents/CODING/src-cross/clang/llvm-3.7.0.src/unittests/Support/ProgramTest.cpp:62:18: error: 
  use of undeclared identifier '_NSGetEnviron'
char **envp = *_NSGetEnviron();
               ^

that I fixed by simply putting char **envp = NULL; (drastic). The make went then like a charm, as well as obvioulsy the sudo make install. Then I scped the whole directory to my iPad, and tried /usr/local/llvm-ios/bin/clang which told me... clang: error: no input files. Success. ;-) Now, as the install is naked, I need to find all standard libraries (iostream etc)...

EDIT, 2015-10-17. After Thomas suggested it I tried this (just used 8.4 instead of 8.3 sdk as my jailbroken ipad mini 3 wifi is under iOS 8.4) :

curl -O http://llvm.org/releases/3.7.0/llvm-3.7.0.src.tar.xz
tar -Jxf llvm-3.7.0.src.tar.xz
cd llvm-3.7.0.src/tools/
curl -O http://llvm.org/releases/3.7.0/cfe-3.7.0.src.tar.xz
tar -Jxf cfe-3.7.0.src.tar.xz
mv cfe-3.7.0.src clang
cd ..
export CC="clang -arch arm64 -mios-version-min=8.4 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.4.sdk"
export CXX="clang++ -arch arm64 -mios-version-min=8.4 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.4.sdk"
mkdir build && cd build

To avoid the following error :

/Users/XXX/Documents/CODING/src-cross/clang/llvm-3.7.0.src/utils/unittest/googletest/src/gtest-death-test.cc:40:12: fatal error: 'crt_externs.h' file not found
#  include <crt_externs.h>
           ^

Thomas warns us about in the post How to cross-compile clang/llvm for iOS?, I went to /Users/XXX/Documents/CODING/src-cross/clang/llvm-3.7.0.src/utils/unittest/googletest/src/gtest-death-test.cc and commented the #include <crt_externs.h>. Then I found the char** GetEnviron() function in

#  if GTEST_OS_MAC
inline char** GetEnviron() {
  // When Google Test is built as a framework on MacOS X, the environ variable
  // is unavailable. Apple's documentation (man environ) recommends using
  // _NSGetEnviron() instead.
  return *_NSGetEnviron();
}

and replaced the orignal return *_NSGetEnviron(); with return NULL;. Then I continued with the configure, the unset and the make VERBOSE=1 -j :

../configure --prefix=/usr/local/XXX-cross/llvm-ios --host=arm-apple-darwin11 --enable-optimized --disable-assertions
unset CC CXX
make VERBOSE=1 -j

The latter triggered the following error :

/Users/XXXX/Documents/CODING/src-cross/clang/llvm-3.7.0.src/lib/LineEditor/LineEditor.cpp:17:10: fatal error: 'histedit.h' file not found
#include <histedit.h>
         ^

which I don't know how to tackle...

Initial question. I am trying to cross-compile clang/llvm 3.7.0 for iOS8.x on ipad mini 3, with the help of the following :

How to cross-compile clang/llvm for iOS?

I have tried this :

curl -O http://llvm.org/releases/3.7.0/llvm-3.7.0.src.tar.xz
tar -Jxf llvm-3.7.0.src.tar.xz
cd llvm-3.7.0.src/tools/
curl -O http://llvm.org/releases/3.7/clang-3.7.src.tar.gz
tar -Jxf cfe-3.7.0.src.tar.xz
mv cfe-3.7.0.src clang
cd ..
export CC="clang -arch armv8a -mios-version-min=8.3 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.3.sdk"
export CXX="clang++ -arch armv8a -mios-version-min=8.3 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.3.sdk"
mkdir build && cd build
../configure --prefix=/usr/local/XXX-cross/llvm-ios --host=armv8a-apple-darwin-eabi --enable-optimized --disable-assertions

without success, having the

error: invalid arch name '-arch armv8a'

And I had this kind of error for all arch's and host's I've tried related to my iPad mini 3, for which I found infos here and there.

I had the same kind of problem when I tried to build gcc for my iPad mini 3, and I have the impression that at the moment, whatever compiler I am trying to "cross-build" for this target, the correct host & arch options are not supported.

I am wrong ? I there a way to pass other options dealing with generic/unknown arch's & host's, that with suitable other options, would give me workable llvm-clang on my iPad mini 3 ?

It's -arch arm64 not -arch armv8a, and change --host=armv8a-apple-darwin-eabi to --host=arm-apple-darwin11.

Also -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.3.sdk only makes sense when you are using a Mac to cross compile for iOS.