libtool mistakes mold 2.4.1 as GNU ld 2.4 and wrongly concludes that our
linker does not support anonymous versioning and suppresses some uses of
version scripts. That has been causing subtle compatibility issues with
programs that use libtool to create their .so files.
Here is the code that mistakes our linker as GNU ld:
https://git.savannah.gnu.org/cgit/libtool.git/tree/m4/libtool.m4?h=v2.4.7#n5066
As a workaround, I decided to bump our linker version so that the version
number is sufficiently large. This is admittedly ugly but I think it's the
simplest solution for the problem.
Our ConcurrentMap uses linear probing to find unused hash table entry.
It gives up if 128 consective slots are occupied, and the whole process
dies with the "ConcurrentMap is full" error message. So our hash
function's quality must be high.
For .gdb_index, we used to use gdb_index() to compute keys for the
ConcurrentMap. It turned out that the function's quality is poor,
generating very similar output for short strings.
This commit changes the hash function to xxhash.
Fixes https://issues.chromium.org/issues/40276991#comment5
Previously, mold marked an imported symbol as a strong one if the
symbol came from a DSO and was exported as a strong symbol by the DSO.
This logic resulted in a miscomputation of the weakness bit, causing a
compatibility issue with other linkers.
Now, an imported symbol is marked as strong only when there's at least
one strong reference to it. In other words, if all references to an
imported symbol are weak, the symbol will be imported as a weak one.
Fixes https://github.com/llvm/llvm-project/issues/83080
Prior to this change, links on Windows were failing with:
mold: fatal: <input file>: CreateFileMapping failed: 5
"5" is the Windows error code for ERROR_ACCESS_DENIED.
Use native Windows file API in MappedFile. Create read only mapping with
FILE_MAP_COPY view because the file mapping contents may be modified in
process but should not be written back.
On Windows, it is important that files are opened in "binary" mode to
avoid automatic "text" mode conversions which can result in "corrupted"
input/output.
Previously, mold didn't merge sections with the same name but different
section flags into a single section. This behavior is different from other
linkers and caused a compatibility issue.
Now, mold merges input sections by their names and types.
Fixes https://github.com/rui314/mold/issues/1196
