[Bug ld/17975] Useless FILE entry in symbol table for linker generated symbols

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=17975

--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
A NULL STT_FILE symbol is useful here:

address@hidden pr17975]$ cat foo.s 
    .data
foo:
    .dc.a bar
address@hidden pr17975]$ cat bar.s
    .data
foo:
    .dc.a bar
address@hidden pr17975]$ cat global.s 
    .data
    .hidden foo
    .global foo
foo:
    .dc.a bar
address@hidden pr17975]$ make hidden.so
as   -o foo.o foo.s
as   -o bar.o bar.s
as   -o global.o global.s
./ld -shared   -o hidden.so foo.o bar.o global.o
readelf -sW hidden.so

Symbol table '.dynsym' contains 6 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 00000000002002f0     0 SECTION LOCAL  DEFAULT    7 
     2: 0000000000200308     0 NOTYPE  GLOBAL DEFAULT    7 __bss_start
     3: 0000000000200308     0 NOTYPE  GLOBAL DEFAULT    7 _edata
     4: 0000000000200308     0 NOTYPE  GLOBAL DEFAULT    7 _end
     5: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND bar

Symbol table '.symtab' contains 20 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 00000000000000e8     0 SECTION LOCAL  DEFAULT    1 
     2: 0000000000000118     0 SECTION LOCAL  DEFAULT    2 
     3: 00000000000001a8     0 SECTION LOCAL  DEFAULT    3 
     4: 00000000000001c8     0 SECTION LOCAL  DEFAULT    4 
     5: 0000000000000210     0 SECTION LOCAL  DEFAULT    5 
     6: 0000000000200210     0 SECTION LOCAL  DEFAULT    6 
     7: 00000000002002f0     0 SECTION LOCAL  DEFAULT    7 
     8: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS foo.o
     9: 00000000002002f0     0 NOTYPE  LOCAL  DEFAULT    7 foo
    10: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS bar.o
    11: 00000000002002f8     0 NOTYPE  LOCAL  DEFAULT    7 foo
    12: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS 
    13: 0000000000200210     0 OBJECT  LOCAL  DEFAULT    6 _DYNAMIC
    14: 0000000000200300     0 NOTYPE  LOCAL  DEFAULT    7 foo
    15: 00000000002002f0     0 OBJECT  LOCAL  DEFAULT    7
_GLOBAL_OFFSET_TABLE_
    16: 0000000000200308     0 NOTYPE  GLOBAL DEFAULT    7 __bss_start
    17: 0000000000200308     0 NOTYPE  GLOBAL DEFAULT    7 _edata
    18: 0000000000200308     0 NOTYPE  GLOBAL DEFAULT    7 _end
    19: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND bar
address@hidden pr17975]$ 

But not here

address@hidden pr17975]$ make lib.so
./ld -shared   -o lib.so foo.o bar.o
readelf -sW lib.so

Symbol table '.dynsym' contains 6 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 00000000002002d8     0 SECTION LOCAL  DEFAULT    7 
     2: 00000000002002e8     0 NOTYPE  GLOBAL DEFAULT    7 __bss_start
     3: 00000000002002e8     0 NOTYPE  GLOBAL DEFAULT    7 _edata
     4: 00000000002002e8     0 NOTYPE  GLOBAL DEFAULT    7 _end
     5: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND bar

Symbol table '.symtab' contains 19 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 00000000000000e8     0 SECTION LOCAL  DEFAULT    1 
     2: 0000000000000118     0 SECTION LOCAL  DEFAULT    2 
     3: 00000000000001a8     0 SECTION LOCAL  DEFAULT    3 
     4: 00000000000001c8     0 SECTION LOCAL  DEFAULT    4 
     5: 00000000000001f8     0 SECTION LOCAL  DEFAULT    5 
     6: 00000000002001f8     0 SECTION LOCAL  DEFAULT    6 
     7: 00000000002002d8     0 SECTION LOCAL  DEFAULT    7 
     8: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS foo.o
     9: 00000000002002d8     0 NOTYPE  LOCAL  DEFAULT    7 foo
    10: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS bar.o
    11: 00000000002002e0     0 NOTYPE  LOCAL  DEFAULT    7 foo
    12: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS 
    13: 00000000002001f8     0 OBJECT  LOCAL  DEFAULT    6 _DYNAMIC
    14: 00000000002002d8     0 OBJECT  LOCAL  DEFAULT    7
_GLOBAL_OFFSET_TABLE_
    15: 00000000002002e8     0 NOTYPE  GLOBAL DEFAULT    7 __bss_start
    16: 00000000002002e8     0 NOTYPE  GLOBAL DEFAULT    7 _edata
    17: 00000000002002e8     0 NOTYPE  GLOBAL DEFAULT    7 _end
    18: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND bar
address@hidden pr17975]$

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