- Mac Clang Version
- Clang Include Library
- Mac Update Clang
- Clang Library Search Path
- Clang Library Path Environment Variable
by Angel Leon. March 17, 2015; August 29, 2019. Site http apple.com mac add image files to iphoto library.
Mac Clang Version
On the compilation phase, you will usually need to specify the different include paths so that the interfaces (.h, .hpp) which define structs, classes, constans, and functions can be found.
llvm include paths are passed with
-I/path/to/includes, you can pass as many
-I as you need.
'libc' C Standard Library. Libc is an implementation of the C standard library, targeting C11, C14 and above. All of the code in libc is dual licensed under the MIT license and the UIUC License (a BSD-like license). New Documentation Coming Soon! Clang is a C, C, and Objective-C compiler which encompasses preprocessing, parsing, optimization, code generation, assembly, and linking. Depending on which high-level mode setting is passed, Clang will stop before doing a full link. While Clang is highly integrated, it is important to understand the stages of compilation, to understand how to invoke it. Clang Static Analyzer. The Clang Static Analyzer is a source code analysis tool that finds bugs in C, C, and Objective-C programs. Currently it can be run either from the command line or if you use macOS then within Xcode.When invoked from the command line, it is. Path A list of paths for the Tag Parser to search for headers included by your source files. If omitted, includePath will be used as the path. Searching on these paths is recursive by default. Specify. to indicate non-recursive search. For example: /usr/include will search through all subdirectories while /usr/include/. will not. To build clang with OpenMP support just follow the clang/LLVM compiler's standard build procedure (see Getting Started: Building and Running Clang). To use the newly installed compiler, add the following to your environment. On Mac OS X, replace LDLIBRARYPATH with DYLDLIBRARYPATH.
cl.exe takes include paths with the following syntax:
/I'c:pathtoincludes you can also pass as many as you need.
Some software uses macro definition variables that should be passed during compile time to decide what code to include.
These compilation-time variables are passed using
These compilation time flags are by convention usually put into a single variable named
CXXFLAGS, which is then passed to the compiler as a parameter for convenience when you're building your compilation/make script.
When you compile your .c, or .cpp files, you will end up with object files.These files usually have
.o extensions in Linux, in Windows they might be under
You can create an
.o file for a single or for many source files. Itunes library auto-update mac os x.
Static Library files
When you have several
.o files, you can put them together as a library, a static library. In Linux/Mac these static libraries are simply archive files, or
.a files. In windows, static library files exist under the
They are created like this in Linux/Mac:
ar -cvq libctest.a ctest1.o ctest2.o ctest3.o
libctest.a will contain
They are created like this in Windows:
LIB.EXE /OUT:MYLIB.LIB FILE1.OBJ FILE2.OBJ FILE3.OBJ
When you are creating an executable that needs to make use of a library, if you use these static libraries, the size of your executable will be the sum of all the object files statically linked by the executable. The code is right there along the executable, it's easier to distribute, but again, the size of the executable can be bigger than it needs to.. why? because, sometimes, many of the
.o files, or even the entire
.a file you're linking against might be a standard library that many other programs need.
Shared Libraries (Dynamic Libraries)
So shared or dynamic libraries were invented so that different programs or libraries would make external (shared) references to them, since they're 'shared' the symbols defined in them don't need to be part of your executable or library, your executable contain symbols whose entry points or offset addresses might point to somewhere within themselves, but they will also have symbols whose entry points are expected to exist on shared libraries which need only be loaded once in a single portion of the operating shared memory, thus not just making the size of your executable as small as it needs to be, but you won't need to load the library for every process/program that needs its symbols.
On Linux shared files exist under the
.so (shared object) file extension, on Mac
.dylib (dynamic library), and in Windows they're called
.dll (dynamic link libraries)
Another cool thing about dynamic libraries, is that they can be loaded during runtime, not just linked at compile time. An example of runtime dynamic libraries are browser plugins.
.so files are created like this:
-Wallenables all warnings.
-cmeans compile only, don't run the linker.
-fPICmeans 'Position Independent Code', a requirement for shared libraries in Linux.
-sharedmakes the object file created shareable by different executables.
-Wlpasses a comma separated list of arguments to the linker.
-sonamemeans 'shared object name' to use.
-o <my.so>means output, in this case the output shared library
.dylib files are created like this:
clang -dynamiclib -o libtest.dylib file1.o file2.o -L/some/library/path -lname_of_library_without_lib_prefix
.dll files are created like this:
LINK.EXE /DLL /OUT:MYLIB.DLL FILE1.OBJ FILE2.OBJ FILE3OBJ
Linking to existing libraries
When linking your software you may be faced with a situation on which you want to link against several standard shared libraries.If all the libraries you need exist in a single folder, you can set the
LD_LIBRARY_PATH to that folder. By common standard all shared libraries are prefixed with the word
lib. If a library exists in
LD_LIBRARY_PATH and you want to link against it, you don't need to pass the entire path to the library, you simply pass
-lname and you will link your executable to the symbols of
libname.so which should be somewhere inside
Tip: You should probably stay away from altering your
LD_LIBRARY_PATH, if you do, make sure you keep its original value, and when you're done restore it, as you might screw the build processes of other software in the system which might depend on what's on the
Clang Include Library
What if libraries are in different folders?
If you have some other
libbar.so library on another folder outside
LD_LIBRARY_PATH you can explictly pass the full path to that library
/path/to/that/other/library/libbar.so, or you can specify the folder that contains it
-L/path/to/that/other/library and then the short hand form
-lbar. This latter option makes more sense if the second folder contains several other libraries.
Sometimes you may be dealing with issues like
undefined symbol errors, and you may want to inspect what symbols (functions) are defined in your library.
On Mac there's
otool, on Linux/Mac there's
nm, on Windows there's
depends.exe (a GUI tool that can be used to see both dependencies and the symbol's tables. Taking a look at the 'Entry Point' column will help you understand clearly the difference between symbols linking to a shared library vs symbols linking statically to the same library)
Useful command options
See shared library dependencies on Mac with
See shared symbols with
nm (Linux/Mac)With nm, you can see the symbol's name list.Familiarize yourself with the meaning of the symbol types:
T(text section symbol)
U(undefined - useful for those
If the symbol is local (non-external) the symbol type is presented in lowercase letters, for example a lowercase
u represents an undefined reference to a private external in another module in the same library.
nm's documentation says that if you're working on Mac and you see that the symbol is preceeded by
- it means it's an ObjectiveC method, if you're familiar with ObjectiveC you will know that
+ is for class methods and
- is for instance methods, but in practice it seems to be a bit more explicit and you will often see
OBJC prefixed to those methods.
nm is best used along with
Find all Undefined symbols
My C++ code compiles but it won't link
Mac Update Clang
Linking is simply 'linking' a bunch of .o files to make an executable.
Each one of these .o's may be compiled on their own out of their .cpp files, but when one references symbols that are supposed to exist in other .o's and they're not to be found then you get linking errors.
Perhaps through forward declarations you managed your compilation phase to pass, but then you get a bunch of symbol not found errors.Make sure to read them slowly, see where these symbols are being referenced, you will see that these issues occur due to namespace visibility in most cases.
Clang Library Search Path
Perhaps you copied the signature of a method that exists in a private space elsewhere into some other namespace where your code wasn't compiling, all you did was make it compilable, but the actual symbol might not be visible outside the scope where it's truly defined and implemented.
Function symbols can be private if they're declared inside anonymous namespaces, or if they're declared as
Here, when I read the code of
Network::TxMessage::handle(..) there was a call to
FlushStateToDisk, which was declared in
main.h, and coded in
TxMessage.cpp did include
main.h, compilation was fine, I had a
TxMessage.o file and a
main.o, but the linker was complaining.
Clang Library Path Environment Variable
The issue was that
FlushStateToDisk was declared as a
static, therefore only visible inside
main.o, once I removed the
static from the declaration and implementation the error went away and my executable was linked. Similar things happen when functions are declared in anonymous spaces in other files, even if you forward declare them on your local
In other cases your code compiles and you get this error linking because your library can't be added using -lfoo, and adding its containing folder to -L doesn't cut it, in this case you just add the full path to the library in your compilation command:
gcc /path/to/the/missing/library.o .. my_source.cpp -o my_executable
DO NOT EXPORT CFLAGS, CPPFLAGS and the like on your
.bashrc, it can lead to unintended building consequences in many projects. I've wasted so many hours due to this mistake.