Stephan Bergmann
e4b24dba07
...which had been replaced with -gsplit-dwarf in
8ecdff7ac3 "Modernize wasm debug symbol
generation". But -gseparate-dwarf and -gsplit-dwarf are apparently orthogonal:
-gseparate-dwarf adds a supplementary *.wasm.debug.wasm (whose relative URL is
recorded in an external_debug_info section in the original *.wasm), and the
original *.wasm and the supplementary *.wasm.debug.wasm have exactly the same
content, except that only the supplementary *.wasm.debug.wasm contains any of
the .debug_* sections (and only the original *.wasm contains the
external_debug_info section). That way, the original *.wasm stays small (so
that it does not exceed any limits of the browser's JS WebAssembly instantiation
machinery), while the browser's debugger (like Chrome's "C/C++ DevTools Support
(DWARF)" extension) uses the supplementary *.wasm.debug.wasm. This is
especially relevant when building LO with e.g. -fsanitize=address, where the
resulting soffice.wasm would otherwise easily grow too large.
-gsplit-dwarf, on the other hand, leaves certain debug information in .debug_*
sections in the original *.wasm and offloads further debug data to an auxiliary
*.wasm.dwp (which the browser's debugger will then load and use in addition to
using the original *.wasm's debug information). When combined with
-gseparate-dwarf, there's an overall three files now: the original *.wasm (used
by the browser's JS WebAssembly instantiation machinery; lacking any debug
information), the supplementary *.wasm.debug.wasm (used by the browser's
debugger; containing some debug information), and the auxiliary
*.wasm.debug.wasm.dwp (used by the browser's debugger; containing further debug
information). (One might assume that when using -gseparate-dwarf there would be
no benefit from additionally using -gsplit-dwarf. But when I tried that with at
least Chrome version 138.0.7204.100 and the "C/C++ DevTools Support (DWARF)"
extension version 0.2.5854.1, it would still sometimes fail with
> [C/C++ DevTools Support (DWARF)] Loading debug symbols for http://localhost:6931/soffice.wasm (via soffice.wasm.debug.wasm)…
> [C/C++ DevTools Support (DWARF)] Failed to load debug symbols for http://localhost:6931/soffice.wasm (TypeError: Failed to fetch)
and the emrun server reporting
> 127.0.0.1 - - [15/Jul/2025 22:41:58] code 404, message File not found: /home/sberg/cowasm/core/workdir/installation/LibreOffice/emscripten/soffice.wasm.debug.wasm.dwp
> 127.0.0.1 - - [15/Jul/2025 22:41:58] "GET /soffice.wasm.debug.wasm.dwp HTTP/1.1" 404 -
making it look like it wanted to access a non-existing auxiliary
soffice.wasm.debug.wasm.dwp for some unclear reason. So, at least for now, it
looks better to just use a setup that provides that auxiliary file anyway.)
Change-Id: I72352479c864c8d89cc63cc228aa676c7c2d8ccf
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/187953
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <stephan.bergmann@collabora.com>
LibreOffice
LibreOffice is an integrated office suite based on copyleft licenses and compatible with most document formats and standards. Libreoffice is backed by The Document Foundation, which represents a large independent community of enterprises, developers and other volunteers moved by the common goal of bringing to the market the best software for personal productivity. LibreOffice is open source, and free to download, use and distribute.
A quick overview of the LibreOffice code structure.
Overview
You can develop for LibreOffice in one of two ways, one recommended and one much less so. First the somewhat less recommended way: it is possible to use the SDK to develop an extension, for which you can read the API docs and Developers Guide. This re-uses the (extremely generic) UNO APIs that are also used by macro scripting in StarBasic.
The best way to add a generally useful feature to LibreOffice is to work on the code base however. Overall this way makes it easier to compile and build your code, it avoids any arbitrary limitations of our scripting APIs, and in general is far more simple and intuitive - if you are a reasonably able C++ programmer.
The Build Chain and Runtime Baselines
These are the current minimal operating system and compiler versions to run and compile LibreOffice, also used by the TDF builds:
- Windows:
- Runtime: Windows 10
- Build: Cygwin + Visual Studio 2019 version 16.10
- macOS:
- Runtime: 11
- Build: 13 or later + Xcode 14.3 or later (using latest version available for a given version of macOS)
- Linux:
- Runtime: RHEL 8 or CentOS 8 and comparable
- Build: either GCC 12; or Clang 12 with libstdc++ 10
- iOS (only for LibreOfficeKit):
- Runtime: 14.5 (only support for newer i devices == 64 bit)
- Build: Xcode 12.5 and iPhone SDK 14.5
- Android:
- Build: NDK 27 and SDK 30.0.3
- Emscripten / WASM:
- Runtime: a browser with SharedMemory support (threads + atomics)
- Build: Qt 5.15 with Qt supported Emscripten 1.39.8
- See README.wasm
Java is required for building many parts of LibreOffice. In TDF Wiki article Development/Java, the exact modules that depend on Java are listed.
The baseline for Java is Java Development Kit (JDK) Version 17 or later.
The baseline for Python is version 3.11. It follows the version available in SUSE Linux Enterprise Desktop and the Maintenance Support version of Red Hat Enterprise Linux.
If you want to use Clang with the LibreOffice compiler plugins, the minimal version of Clang is 12.0.1. Since Xcode doesn't provide the compiler plugin headers, you have to compile your own Clang to use them on macOS.
You can find the TDF configure switches in the distro-configs/ directory.
To setup your initial build environment on Windows and macOS, we provide the LibreOffice Development Environment (LODE) scripts.
For more information see the build instructions for your platform in the TDF wiki.
The Important Bits of Code
Each module should have a README.md file inside it which has some
degree of documentation for that module; patches are most welcome to
improve those. We have those turned into a web page here:
However, there are two hundred modules, many of them of only peripheral interest for a specialist audience. So - where is the good stuff, the code that is most useful. Here is a quick overview of the most important ones:
| Module | Description |
|---|---|
| sal/ | this provides a simple System Abstraction Layer |
| tools/ | this provides basic internal types: Rectangle, Color etc. |
| vcl/ | this is the widget toolkit library and one rendering abstraction |
| framework/ | UNO framework, responsible for building toolbars, menus, status bars, and the chrome around the document using widgets from VCL, and XML descriptions from /uiconfig/ files |
| sfx2/ | legacy core framework used by Writer/Calc/Draw: document model / load/save / signals for actions etc. |
| svx/ | drawing model related helper code, including much of Draw/Impress |
Then applications
| Module | Description |
|---|---|
| desktop/ | this is where the main() for the application lives, init / bootstrap. the name dates back to an ancient StarOffice that also drew a desktop |
| sw/ | Writer |
| sc/ | Calc |
| sd/ | Draw / Impress |
There are several other libraries that are helpful from a graphical perspective:
| Module | Description |
|---|---|
| basegfx/ | algorithms and data-types for graphics as used in the canvas |
| canvas/ | new (UNO) canvas rendering model with various backends |
| cppcanvas/ | C++ helper classes for using the UNO canvas |
| drawinglayer/ | View code to render drawable objects and break them down into primitives we can render more easily. |
Rules for #include Directives (C/C++)
Use the "..." form if and only if the included file is found next to the
including file. Otherwise, use the <...> form. (For further details, see the
mail Re: C[++]: Normalizing include syntax ("" vs
<>).)
The UNO API include files should consistently use double quotes, for the benefit of external users of this API.
loplugin:includeform (compilerplugins/clang/includeform.cxx) enforces these rules.
Finding Out More
Beyond this, you can read the README.md files, send us patches, ask
on the mailing list libreoffice@lists.freedesktop.org (no subscription
required) or poke people on IRC #libreoffice-dev on irc.libera.chat -
we're a friendly and generally helpful mob. We know the code can be
hard to get into at first, and so there are no silly questions.
SAST Tools
PVS-Studio - static analyzer for C, C++, C#, and Java code.