https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95095
Bug ID: 95095
Summary: Feature request: support -fno-unique-section-names
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: i at maskray dot me
Target Milestone: ---
-ffunction-sections produces sections .text.foo , .text.bar , etc, which can
take significant amount of string table space.
In clang, -fno-unique-section-names emits multiple ".text" sections which can
share the section name. Multiple sections with the same name require the new
GNU as feature https://sourceware.org/bugzilla/show_bug.cgi?id=25380 (binutils
2.35).
For .text.exit.* .text.unlikely.* .text.hot.* .text.startup.* , the preferred
sections are .text.exit. .text.unlikely. .text.hot. .text.startup. The trailing
dots can avoid a linker problem described in https://reviews.llvm.org/D79600
--------- pasted below for your convenience
GNU ld's internal linker script uses
(https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=add44f8d5c5c05e08b11e033127a744d61c26aee)
.text :
{
*(.text.unlikely .text.*_unlikely .text.unlikely.*)
*(.text.exit .text.exit.*)
*(.text.startup .text.startup.*)
*(.text.hot .text.hot.*)
*(SORT(.text.sorted.*))
*(.text .stub .text.* .gnu.linkonce.t.*)
/* .gnu.warning sections are handled specially by elf.em. */
*(.gnu.warning)
}
Because *(.text.exit .text.exit.*) is ordered before *(.text .text.*), in a
-ffunction-sections build, the C library function exit will be placed before
other functions.
gold's -z keep-text-section-prefix has the same problem.
In lld, -z keep-text-section-prefix recognizes
.text.{exit,hot,startup,unlikely,unknown}.*, but not
.text.{exit,hot,startup,unlikely,unknown}, to avoid the strange placement
problem.
