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update readme to use mimalloc.dll (instead of mimalloc-override.dll)

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Daan Leijen 2024-12-20 12:52:34 -08:00
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@ -428,43 +428,48 @@ Note that certain security restrictions may apply when doing this from
the [shell](https://stackoverflow.com/questions/43941322/dyld-insert-libraries-ignored-when-calling-application-through-bash).
### Dynamic Override on Windows
# Windows Override
<span id="override_on_windows">Dynamically overriding on mimalloc on Windows</span>
is robust and has the particular advantage to be able to redirect all malloc/free calls that go through
the (dynamic) C runtime allocator, including those from other DLL's or libraries.
As it intercepts all allocation calls on a low level, it can be used reliably
is robust and has the particular advantage to be able to redirect all malloc/free calls
that go through the (dynamic) C runtime allocator, including those from other DLL's or
libraries. As it intercepts all allocation calls on a low level, it can be used reliably
on large programs that include other 3rd party components.
There are four requirements to make the overriding work robustly:
There are four requirements to make the overriding work well:
1. Use the C-runtime library as a DLL (using the `/MD` or `/MDd` switch).
2. Link your program explicitly with `mimalloc-override.dll` library.
To ensure the `mimalloc-override.dll` is loaded at run-time it is easiest to insert some
call to the mimalloc API in the `main` function, like `mi_version()`
(or use the `/INCLUDE:mi_version` switch on the linker). See the `mimalloc-override-test` project
for an example on how to use this.
3. The [`mimalloc-redirect.dll`](bin) (or `mimalloc-redirect32.dll`) must be put
in the same folder as the main `mimalloc-override.dll` at runtime (as it is a dependency of that DLL).
The redirection DLL ensures that all calls to the C runtime malloc API get redirected to
mimalloc functions (which reside in `mimalloc-override.dll`).
4. Ensure the `mimalloc-override.dll` comes as early as possible in the import
2. Link your program explicitly with the `mimalloc.lib` export library for the `mimalloc.dll`.
(which must be compiled with `-DMI_OVERRIDE=ON`, which is the default though).
To ensure the `mimalloc.dll` is actually loaded at run-time it is easiest
to insert some call to the mimalloc API in the `main` function, like `mi_version()`
(or use the `/include:mi_version` switch on the linker command, or
similarly, `#pragma comment(linker, "/include:mi_version")` in some source file).
See the `mimalloc-test-override` project for an example on how to use this.
3. The `mimalloc-redirect.dll` must be put in the same folder as the main
`mimalloc.dll` at runtime (as it is a dependency of that DLL).
The redirection DLL ensures that all calls to the C runtime malloc API get
redirected to mimalloc functions (which reside in `mimalloc.dll`).
4. Ensure the `mimalloc.dll` comes as early as possible in the import
list of the final executable (so it can intercept all potential allocations).
You can use `minject -l <exe>` to check this if needed.
For best performance on Windows with C++, it
is also recommended to also override the `new`/`delete` operations (by including
[`mimalloc-new-delete.h`](include/mimalloc-new-delete.h)
[`mimalloc-new-delete.h`](../include/mimalloc-new-delete.h)
a single(!) source file in your project).
The environment variable `MIMALLOC_DISABLE_REDIRECT=1` can be used to disable dynamic
overriding at run-time. Use `MIMALLOC_VERBOSE=1` to check if mimalloc was successfully redirected.
overriding at run-time. Use `MIMALLOC_VERBOSE=1` to check if mimalloc was successfully
redirected.
For different platforms than x64, you may need a specific [redirection dll](bin).
Furthermore, we cannot always re-link an executable or ensure `mimalloc.dll` comes
first in the import table. In such cases the [`minject`](bin) tool can be used
to patch the executable's import tables.
We cannot always re-link an executable with `mimalloc-override.dll`, and similarly, we cannot always
ensure the the DLL comes first in the import table of the final executable.
In many cases though we can patch existing executables without any recompilation
if they are linked with the dynamic C runtime (`ucrtbase.dll`) -- just put the `mimalloc-override.dll`
into the import table (and put `mimalloc-redirect.dll` in the same folder)
Such patching can be done for example with [CFF Explorer](https://ntcore.com/?page_id=388) or
the [`minject`](bin) program.
## Static override