3.17.2 Darwin Options
These options are defined for all architectures running the Darwin operating system.
FSF GCC on Darwin does not create “universal” object files; it will create an object file for the single architecture that it was built to target. Apple's GCC on Darwin does create “universal” files if multiple -arch options are used; it does so by running the compiler or linker multiple times and joining the results together with lipo.
The subtype of the file created (like `ppc7400' or `ppc970' or `i686') is determined by the flags that specify the ISA that GCC is targetting, like -mcpu or -march. The -force_cpusubtype_ALL option can be used to override this.
The Darwin tools vary in their behavior when presented with an ISA mismatch. The assembler, as, will only permit instructions to be used that are valid for the subtype of the file it is generating, so you cannot put 64-bit instructions in an `ppc750' object file. The linker for shared libraries, /usr/bin/libtool, will fail and print an error if asked to create a shared library with a less restrictive subtype than its input files (for instance, trying to put a `ppc970' object file in a `ppc7400' library). The linker for executables, ld, will quietly give the executable the most restrictive subtype of any of its input files.
- Add the framework directory dir to the head of the list of
directories to be searched for header files. These directories are
interleaved with those specified by -I options and are
scanned in a left-to-right order.
A framework directory is a directory with frameworks in it. A framework is a directory with a `"Headers"' and/or `"PrivateHeaders"' directory contained directly in it that ends in `".framework"'. The name of a framework is the name of this directory excluding the `".framework"'. Headers associated with the framework are found in one of those two directories, with `"Headers"' being searched first. A subframework is a framework directory that is in a framework's `"Frameworks"' directory. Includes of subframework headers can only appear in a header of a framework that contains the subframework, or in a sibling subframework header. Two subframeworks are siblings if they occur in the same framework. A subframework should not have the same name as a framework, a warning will be issued if this is violated. Currently a subframework cannot have subframeworks, in the future, the mechanism may be extended to support this. The standard frameworks can be found in `"/System/Library/Frameworks"' and `"/Library/Frameworks"'. An example include looks like
#include <Framework/header.h>, where `Framework' denotes the name of the framework and header.h is found in the `"PrivateHeaders"' or `"Headers"' directory.
- Like -F except the directory is a treated as a system
directory. The main effect is to not warn about constructs contained
within header files found via dir.
- Emit debugging information for symbols that are used. For STABS
debugging format, this enables -feliminate-unused-debug-symbols.
This is by default ON.
- Emit debugging information for all symbols and types.
- The earliest version of MacOS X that this executable will run on
is version. Typical values of version include
If the compiler was built to use the system's headers by default, then the default for this option is the system version on which the compiler is running, otherwise the default is to make choices which are compatible with as many systems and code bases as possible.
- Enable kernel development mode. The -mkernel option sets
-static, -fno-common, -fno-cxa-atexit,
-fapple-kext, -fno-weak and -fno-rtti where
applicable. This mode also sets -mno-altivec,
-msoft-float, -fno-builtin and
-mlong-branch for PowerPC targets.
- Override the defaults for `bool' so that `sizeof(bool)==1'.
By default `sizeof(bool)' is `4' when compiling for
Darwin/PowerPC and `1' when compiling for Darwin/x86, so this
option has no effect on x86.
Warning: The -mone-byte-bool switch causes GCC to generate code that is not binary compatible with code generated without that switch. Using this switch may require recompiling all other modules in a program, including system libraries. Use this switch to conform to a non-default data model.
- Generate code suitable for fast turn around development. Needed to
enable gdb to dynamically load
.ofiles into already running programs. -findirect-data and -ffix-and-continue are provided for backwards compatibility.
Alter vtables, destructors, and other implementation details to more
closely resemble the GCC 2.95 ABI. This is to make kernel extensions
loadable by Darwin kernels, and is required to build any Darwin kernel
extension. In addition, virtual calls are not made directly, instead,
code is generated to always go through the virtual table, as virtual
tables can be patched by the kernel module loader. Vtables are
altered by adding a zero word at the end of every vtable.
-fno-exceptions and -static must also be used with
this flag. -findirect-virtual-calls and
-fterminated-vtables are accepted for backwards compatibility
but will be removed in the future.
- Allow Pascal-style string literals to be constructed. This option
implies -Wpointer-sign so that conversions between
Pascal-style strings and C-style strings are warned about. (APPLE
See Constructing String Literals with a Pascal-style Length Byte, for more information on the syntax and semantics of Pascal string literals.
- Loads all members of static archive libraries.
See man ld(1) for more information.
- Cause the errors having to do with files that have the wrong architecture
to be fatal.
- Causes the output file to be marked such that the dynamic linker will
bind all undefined references when the file is loaded or launched.
- Produce a Mach-o bundle format file.
See man ld(1) for more information.
- This option specifies the executable that will be loading the build
output file being linked. See man ld(1) for more information.
- When passed this option, GCC will produce a dynamic library instead of
an executable when linking, using the Darwin libtool command.
- This causes GCC's output file to have the ALL subtype, instead of
one controlled by the -mcpu or -march option.
- These options are passed to the Darwin linker. The Darwin linker man page describes them in detail.