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[ELF] Remove unused synthetic sections from script commands

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Script commands are processed before unused synthetic sections are
removed. Therefore, if a linker script matches one of these sections
it'll get emitted as an empty output section because the logic for
removing unused synthetic sections ignores script commands which
could have already matched and captured one of these sections. This
patch fixes that by also removing the unused synthetic sections from
the script commands.

Differential Revision: https://reviews.llvm.org/D34800

llvm-svn: 307037
This commit is contained in:
Petr Hosek 2017-07-03 15:49:25 +00:00
parent d7a1c334ce
commit 52db9a4fe6
2 changed files with 28 additions and 1 deletions
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11
lld/ELF/Writer.cpp
View File

@ -1149,8 +1149,17 @@ static void removeUnusedSyntheticSections(std::vector<OutputSection *> &V) {
SS->Live = false;
// If there are no other sections in the output section, remove it from the
// output.
if (OS->Sections.empty())
if (OS->Sections.empty()) {
V.erase(std::find(V.begin(), V.end(), OS));
// Also remove script commands matching the output section.
auto &Cmds = Script->Opt.Commands;
auto I = std::remove_if(Cmds.begin(), Cmds.end(), [&](BaseCommand *Cmd) {
if (auto *OSCmd = dyn_cast<OutputSectionCommand>(Cmd))
return OSCmd->Sec == OS;
return false;
});
Cmds.erase(I, Cmds.end());
}
}
}

18
lld/test/ELF/linkerscript/unused-synthetic.s Normal file
View File

@ -0,0 +1,18 @@
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
# RUN: echo "SECTIONS { \
# RUN: .got : { *(.got) } \
# RUN: .plt : { *(.plt) } \
# RUN: .text : { *(.text) } \
# RUN: }" > %t.script
# RUN: ld.lld -shared -o %t.so --script %t.script %t.o
# RUN: llvm-objdump -section-headers %t.so | FileCheck %s
# CHECK-NOT: .got
# CHECK-NOT: .plt
# CHECK: .text
# CHECK-NEXT: .dynsym
.global _start
_start:
nop