我最近使用Macports将Snow Leopard Mac上的gcc从4.2升级到4.7。 Intallation很好，完全成功。我打开终端进行测试，两个相同的版本，一个工作，一个不工作。看看：
iMac:bin john$ cp x86_64-apple-darwin10-gcc-4.7.4 gcc
cp: gcc and x86_64-apple-darwin10-gcc-4.7.4 are identical (not copied).
iMac:bin john$ gcc --help
gcc-mp-4.7: error trying to exec '/opt/local/bin/i686-apple-darwin10-gcc-4.2.1': execvp: No such file or directory
iMac:bin john$ x86_64-apple-darwin10-gcc-4.7.4 --help
Usage: x86_64-apple-darwin10-gcc-4.7.4 [options] file...
Options:
-pass-exit-codes Exit with highest error code from a phase
--help Display this information
--target-help Display target specific command line options
--help={common|optimizers|params|target|warnings|[^]{joined|separate|undocumented}}[,...]
Display specific types of command line options
(Use '-v --help' to display command line options of sub-processes)
--version Display compiler version information
-dumpspecs Display all of the built in spec strings
-dumpversion Display the version of the compiler
-dumpmachine Display the compiler's target processor
-print-search-dirs Display the directories in the compiler's search path
-print-libgcc-file-name Display the name of the compiler's companion library
-print-file-name=<lib> Display the full path to library <lib>
-print-prog-name=<prog> Display the full path to compiler component <prog>
-print-multiarch Display the target's normalized GNU triplet, used as
a component in the library path
-print-multi-directory Display the root directory for versions of libgcc
-print-multi-lib Display the mapping between command line options and
multiple library search directories
-print-multi-os-directory Display the relative path to OS libraries
-print-sysroot Display the target libraries directory
-print-sysroot-headers-suffix Display the sysroot suffix used to find headers
-Wa,<options> Pass comma-separated <options> on to the assembler
-Wp,<options> Pass comma-separated <options> on to the preprocessor
-Wl,<options> Pass comma-separated <options> on to the linker
-Xassembler <arg> Pass <arg> on to the assembler
-Xpreprocessor <arg> Pass <arg> on to the preprocessor
-Xlinker <arg> Pass <arg> on to the linker
-save-temps Do not delete intermediate files
-save-temps=<arg> Do not delete intermediate files
-no-canonical-prefixes Do not canonicalize paths when building relative
prefixes to other gcc components
-pipe Use pipes rather than intermediate files
-time Time the execution of each subprocess
-specs=<file> Override built-in specs with the contents of <file>
-std=<standard> Assume that the input sources are for <standard>
--sysroot=<directory> Use <directory> as the root directory for headers
and libraries
-B <directory> Add <directory> to the compiler's search paths
-v Display the programs invoked by the compiler
-### Like -v but options quoted and commands not executed
-E Preprocess only; do not compile, assemble or link
-S Compile only; do not assemble or link
-c Compile and assemble, but do not link
-o <file> Place the output into <file>
-pie Create a position independent executable
-shared Create a shared library
-x <language> Specify the language of the following input files
Permissible languages include: c c++ assembler none
'none' means revert to the default behavior of
guessing the language based on the file's extension
Options starting with -g, -f, -m, -O, -W, or --param are automatically
passed on to the various sub-processes invoked by x86_64-apple-darwin10-gcc-4.7.4. In order to pass
other options on to these processes the -W<letter> options must be used.
For bug reporting instructions, please see:
<https://trac.macports.org/newticket>.
iMac:bin john$
根据操作系统，gcc（简写）及其完整文件是相同的，这是有道理的。但是当我使用速记测试gcc时，有一个奇怪的错误，看起来4.2版本的更新存在问题。当我用完整的文件测试它（再次，与速记相同），它的工作原理。这怎么可能，如果你能说出gcc有什么问题，我该怎样做才能让gcc从命令行再次运行？