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[ELF] Make SORT_INIT_PRIORITY support .ctors.N

Authored by MaskRay on Nov 12 2020, 8:56 AM.

Description

[ELF] Make SORT_INIT_PRIORITY support .ctors.N

Input sections .ctors/.ctors.N may go to either the output section .init_array or the output section .ctors:

  • output .ctors: currently we sort them by name. This patch changes to sort by priority from high to low. If N in .ctors.N is in the form of %05u, there is no semantic difference. Actually GCC and Clang do use %05u. (In the test ctors_dtors_priority.s and Gold's test gold/testsuite/script_test_14.s, we can see %03u, but they are not really produced by compilers.)
  • output .init_array: users can provide an input section description SORT_BY_INIT_PRIORITY(.init_array.* .ctors.*) to mix .init_array.* and .ctors.*. This can make .init_array.N and .ctors.(65535-N) interchangeable.

With this change, users can mix .ctors.N and .init_array.N in .init_array (PR44698 and PR48096) with linker scripts. As an example:

SECTIONS {
  .init_array : {
    *(SORT_BY_INIT_PRIORITY(.init_array.* .ctors.*))
    *(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .ctors)
  }
} INSERT AFTER .fini_array;
SECTIONS {
  .fini_array : {
    *(SORT_BY_INIT_PRIORITY(.fini_array.* .dtors.*))
    *(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .dtors)
  }
} INSERT BEFORE .init_array;

Reviewed By: psmith

Differential Revision: https://reviews.llvm.org/D91187

Details

Committed
MaskRayNov 12 2020, 8:56 AM
Reviewer
psmith
Differential Revision
D91187: [ELF] Make SORT_INIT_PRIORITY support .ctors.N
Parents
rG73d01a80cec3: [ELF] Sort by input order within an input section description
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