[ELF] - Do not set st_size field of SHT_UNDEF symbols.
This fixes PR33598.
Size field for undefined symbols is not significant.
Setting it to fixed value, like zero, may be useful though.
For example when we have 2 DSO's, like in this PR, if lower level DSO may
change slightly (in part of some symbol's st_size) and higher-level DSO is
rebuilt, then tools that monitoring checksum of high level DSO file can notice
it and trigger cascade of some other unnecessary actions.
If we set st_size to zero, that can be avoided.
Differential revision: https://reviews.llvm.org/D34673
llvm-svn: 306526
diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
index cb1494d..4c5b4f3 100644
--- a/lld/ELF/SyntheticSections.cpp
+++ b/lld/ELF/SyntheticSections.cpp
@@ -1376,7 +1376,6 @@
}
ESym->st_name = Ent.StrTabOffset;
- ESym->st_size = Body->getSize<ELFT>();
// Set a section index.
if (const OutputSection *OutSec = Body->getOutputSection())
@@ -1386,6 +1385,14 @@
else if (isa<DefinedCommon>(Body))
ESym->st_shndx = SHN_COMMON;
+ // Copy symbol size if it is a defined symbol. st_size is not significant
+ // for undefined symbols, so whether copying it or not is up to us if that's
+ // the case. We'll leave it as zero because by not setting a value, we can
+ // get the exact same outputs for two sets of input files that differ only
+ // in undefined symbol size in DSOs.
+ if (ESym->st_shndx != SHN_UNDEF)
+ ESym->st_size = Body->getSize<ELFT>();
+
// st_value is usually an address of a symbol, but that has a
// special meaining for uninstantiated common symbols (this can
// occur if -r is given).