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On Fri, 17 Oct 2008 11:11:21 -0700 (PDT) |
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ann kok <annkok2001@×××××.com> wrote: |
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> hi all |
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Hello, |
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|
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> why we have to put the following flags in the make.conf |
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> |
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> what are the purpose? |
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> |
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> CFLAGS="-O2 -pipe" |
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> CXXFLAGS="-O2 -pipe" |
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> CHOST="x86_64-pc-linux-gnu" |
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|
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These are parameters for the gcc compiler. On a Gentoo system, you |
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compile all (or most of) your software from source, instead of simply |
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installing a precompiled binary package, as in most other distributions. |
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|
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These parameters influence the compiler, the software which actually |
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builds the program from the source code. Their exact meaning is |
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documented in gcc's manual page (man gcc). |
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|
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-O2 instructs the compiler to perform second level optimizations on the |
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code (note 'O', not '0'). |
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-pipe tells gcc to use unix pipes for communication during the compile |
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process, which might speed up things. |
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|
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CFLAGS specifies the options when compiling a C source file, CXXFLAGS |
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is for C++ files. |
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|
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CHOST specifies your machine architecture and operating system type. |
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This stems from the GNU config package which is used by the |
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automake/autoconf build system which is used for most software. |
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According to config.sub from autoconf, the format of this target |
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specification is: |
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|
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# CPU_TYPE-MANUFACTURER-OPERATING_SYSTEM |
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# or in some cases, the newer four-part form: |
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# CPU_TYPE-MANUFACTURER-KERNEL-OPERATING_SYSTEM |
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|
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Cheers, |
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Patric |
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