[ELF] - Stop setting OutSecOff too early.

Currently LLD sets OutSecOff in addSection for input sections.
That is a fake offset (just a rude approximation to remember the order), 
used for sorting SHF_LINK_ORDER sections
(see resolveShfLinkOrder, compareByFilePosition).

There are 2 problems with such approach:

1. We currently change and reuse Size field as a value assigned. Changing size is
not good because leads to bugs. Currently, SIZEOF(.bss) for empty .bss returns 2
because we add two empty synthetic sections and increase size twice by 1. 
(See PR37011: https://bugs.llvm.org/show_bug.cgi?id=37011)

2. Such approach simply does not work when --symbol-ordering-file is involved,
because processing of the ordering file might break the initial section order.

This fixes PR37011.

Differential revision: https://reviews.llvm.org/D45368

llvm-svn: 329560

1 files changed, 2 insertions, 3 deletions

diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 15751b876e0..7d372aca650 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -777,9 +777,8 @@ void LinkerScript::assignOffsets(OutputSection *Sec) {
   if (PhdrEntry *L = Ctx->OutSec->PtLoad)
     L->LMAOffset = Ctx->LMAOffset;
 
-  // The Size previously denoted how many InputSections had been added to this
-  // section, and was used for sorting SHF_LINK_ORDER sections. Reset it to
-  // compute the actual size value.
+  // We can call this method multiple times during the creation of
+  // thunks and want to start over calculation each time.
   Sec->Size = 0;
 
   // We visited SectionsCommands from processSectionCommands to