Why are some libc symbols WEAK and others GLOBAL?

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Why are different symbols in libc declared with different visibility levels,



1510 0x0003d200 0xf7d55200 WEAK FUNC 55 system
 454 0x00067b40 0xf7d7fb40 WEAK FUNC 474 puts
 147 0x000303d0 0xf7d483d0 GLOBAL FUNC 33 exit


From readelf -s /lib/i386-linux-gnu/libc-2.27.so,



 147: 000303d0 33 FUNC GLOBAL DEFAULT 13 exit@@GLIBC_2.0
 454: 00067b40 474 FUNC WEAK DEFAULT 13 puts@@GLIBC_2.0
1510: 0003d200 55 FUNC WEAK DEFAULT 13 system@@GLIBC_2.0


From this question, it seems like the authors' libc has a LOCAL exit?



What the rhyme or reason behind the different libc visibility levels?






ubuntu glibc elf symbol-table






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    up vote
    0
    down vote

    favorite












    Why are different symbols in libc declared with different visibility levels,



    1510 0x0003d200 0xf7d55200 WEAK FUNC 55 system
     454 0x00067b40 0xf7d7fb40 WEAK FUNC 474 puts
     147 0x000303d0 0xf7d483d0 GLOBAL FUNC 33 exit


    From readelf -s /lib/i386-linux-gnu/libc-2.27.so,



     147: 000303d0 33 FUNC GLOBAL DEFAULT 13 exit@@GLIBC_2.0
     454: 00067b40 474 FUNC WEAK DEFAULT 13 puts@@GLIBC_2.0
    1510: 0003d200 55 FUNC WEAK DEFAULT 13 system@@GLIBC_2.0


    From this question, it seems like the authors' libc has a LOCAL exit?



    What the rhyme or reason behind the different libc visibility levels?






    ubuntu glibc elf symbol-table






    share

























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      Why are different symbols in libc declared with different visibility levels,



      1510 0x0003d200 0xf7d55200 WEAK FUNC 55 system
       454 0x00067b40 0xf7d7fb40 WEAK FUNC 474 puts
       147 0x000303d0 0xf7d483d0 GLOBAL FUNC 33 exit


      From readelf -s /lib/i386-linux-gnu/libc-2.27.so,



       147: 000303d0 33 FUNC GLOBAL DEFAULT 13 exit@@GLIBC_2.0
       454: 00067b40 474 FUNC WEAK DEFAULT 13 puts@@GLIBC_2.0
      1510: 0003d200 55 FUNC WEAK DEFAULT 13 system@@GLIBC_2.0


      From this question, it seems like the authors' libc has a LOCAL exit?



      What the rhyme or reason behind the different libc visibility levels?






      ubuntu glibc elf symbol-table






      share















      Why are different symbols in libc declared with different visibility levels,



      1510 0x0003d200 0xf7d55200 WEAK FUNC 55 system
       454 0x00067b40 0xf7d7fb40 WEAK FUNC 474 puts
       147 0x000303d0 0xf7d483d0 GLOBAL FUNC 33 exit


      From readelf -s /lib/i386-linux-gnu/libc-2.27.so,



       147: 000303d0 33 FUNC GLOBAL DEFAULT 13 exit@@GLIBC_2.0
       454: 00067b40 474 FUNC WEAK DEFAULT 13 puts@@GLIBC_2.0
      1510: 0003d200 55 FUNC WEAK DEFAULT 13 system@@GLIBC_2.0


      From this question, it seems like the authors' libc has a LOCAL exit?



      What the rhyme or reason behind the different libc visibility levels?






      ubuntu glibc elf symbol-table




      ubuntu glibc elf symbol-table





      share














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      edited 1 min ago

























      asked 6 mins ago









      Evan Carroll

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