## Purpose
This patch makes a minor changes to LLVM and Clang so that LLVM can be
built as a Windows DLL with `clang-cl`. These changes were not required
for building a Windows DLL with MSVC.
## Background
The Windows DLL effort is tracked in #109483. Additional context is
provided in [this
discourse](https://discourse.llvm.org/t/psa-annotating-llvm-public-interface/85307),
and documentation for `LLVM_ABI` and related annotations is found in the
LLVM repo
[here](https://github.com/llvm/llvm-project/blob/main/llvm/docs/InterfaceExportAnnotations.rst).
## Overview
Specific changes made in this patch:
- Remove `constexpr` fields that reference DLL exported symbols. These
symbols cannot be resolved at compile time when building a Windows DLL
using `clang-cl`, so they cannot be `constexpr`. Instead, they are made
`const` and initialized in the implementation file rather than at
declaration in the header.
- Annotate symbols now defined out-of-line with `LLVM_ABI` so they are
exported when building as a shared library.
- Explicitly add default copy assignment operator for `ELFFile` to
resolve a compiler warning.
## Validation
Local builds and tests to validate cross-platform compatibility. This
included llvm, clang, and lldb on the following configurations:
- Windows with MSVC
- Windows with Clang
- Linux with GCC
- Linux with Clang
- Darwin with Clang
So far CSA was relying on the LLVM Statistic package that allowed us to
gather some data about analysis of an entire translation unit. However,
the translation unit consists of a collection of loosely related entry
points. Aggregating data across multiple such entry points is often
counter productive.
This change introduces a new lightweight always-on facility to collect
Boolean or numerical statistics for each entry point and dump them in a
CSV format. Such format makes it easy to aggregate data across multiple
translation units and analyze it with common data-processing tools.
We break down the existing statistics that were collected on the per-TU
basis into values per entry point.
Additionally, we enable the statistics unconditionally (STATISTIC ->
ALWAYS_ENABLED_STATISTIC) to facilitate their use (you can gather the
data with a simple run-time flag rather than having to recompile the
analyzer). These statistics are very light and add virtually no
overhead.
Co-authored-by: Balazs Benics <benicsbalazs@gmail.com>
CPP-6160
If we have a refutation Z3 query timed out (UNDEF), allow a couple of
retries to improve stability of the query. By default allow 2 retries,
which will give us in maximum of 3 solve attempts per query.
Retries should help mitigating flaky Z3 queries.
See the details in the following RFC:
https://discourse.llvm.org/t/analyzer-rfc-retry-z3-crosscheck-queries-on-timeout/83711
Note that with each attempt, we spend more time per query.
Currently, we have a 15 seconds timeout per query - which are also in
effect for the retry attempts.
---
Why should this help?
In short, retrying queries should bring stability because if a query
runs long
it's more likely that it did so due to some runtime anomaly than it's on
the edge of succeeding. This is because most queries run quick, and the
queries that run long, usually run long by a fair amount.
Consequently, retries should improve the stability of the outcome of the
Z3 query.
In general, the retries shouldn't increase the overall analysis time
because it's really rare we hit the 0.1% of the cases when we would do
retries. But keep in mind that the retry attempts can add up if many
retries are allowed, or the individual query timeout is large.
CPP-5920
This is exactly as originally landed in #95129,
but now the minimal Z3 version was increased to meet this change in #96682.
https://discourse.llvm.org/t/bump-minimal-z3-requirements-from-4-7-1-to-4-8-9/79664/4
---
This patch is a functional change.
https://discourse.llvm.org/t/analyzer-rfc-taming-z3-query-times/79520
As a result of this patch, individual Z3 queries in refutation will be
bound by 300ms. Every report equivalence class will be processed in at
most 1 second.
The heuristic should have only really marginal observable impact -
except for the cases when we had big report eqclasses with long-running
(15s) Z3 queries, where previously CSA effectively halted. After this
patch, CSA will tackle such extreme cases as well.
(cherry picked from commit eacc3b3504be061f7334410dd0eb599688ba103a)
This patch is a functional change.
https://discourse.llvm.org/t/analyzer-rfc-taming-z3-query-times/79520
As a result of this patch, individual Z3 queries in refutation will be
bound by 300ms. Every report equivalence class will be processed in
at most 1 second.
The heuristic should have only really marginal observable impact -
except for the cases when we had big report eqclasses with long-running
(15s) Z3 queries, where previously CSA effectively halted.
After this patch, CSA will tackle such extreme cases as well.
Reviewers: NagyDonat, haoNoQ, Xazax-hun, Szelethus, mikhailramalho
Reviewed By: NagyDonat
Pull Request: https://github.com/llvm/llvm-project/pull/95129
