OLD | NEW |
(Empty) | |
| 1 # Startup |
| 2 |
| 3 Chrome is (mostly) shipped as a single executable that knows how to run as all |
| 4 the interesting sorts of processes we use. |
| 5 |
| 6 Here's an overview of how that works. |
| 7 |
| 8 1. First there's the platform-specific entry point: `wWinMain()` on Windows, |
| 9 `main()` on Linux. This lives in `chrome/app/chrome_exe_main_*`. On Mac and |
| 10 Windows, that function loads modules as described later, while on Linux it |
| 11 does very little, and all of them call into: |
| 12 2. `ChromeMain()`, which is the place where cross-platform code that needs to |
| 13 run in all Chrome processes lives. It lives in `chrome/app/chrome_main*`. |
| 14 For example, here is where we call initializers for modules like logging and |
| 15 ICU. We then examine the internal `--process-type` switch and dispatch to: |
| 16 3. A process-type-specific main function such as `BrowserMain()` (for the outer |
| 17 browser process) or `RendererMain()` (for a tab-specific renderer process). |
| 18 |
| 19 ## Platform-specific entry points |
| 20 |
| 21 ### Windows |
| 22 |
| 23 On Windows we build the bulk of Chrome as a DLL. (XXX: why?) `wWinMain()` |
| 24 loads `chrome.dll`, does some other random stuff (XXX: why?) and calls |
| 25 `ChromeMain()` in the DLL. |
| 26 |
| 27 ### Mac |
| 28 |
| 29 Mac is also packaged as a framework and an executable, but they're linked |
| 30 together: `main()` calls `ChromeMain()` directly. There is also a second entry |
| 31 point, in |
| 32 [`chrome_main_app_mode_mac.mm`](https://cs.chromium.org/chromium/src/chrome/app_
shim/chrome_main_app_mode_mac.mm), |
| 33 for app mode shortcuts: "On Mac, one can't make shortcuts with command-line |
| 34 arguments. Instead, we produce small app bundles which locate the Chromium |
| 35 framework and load it, passing the appropriate |
| 36 data." This executable also calls `ChromeMain()`. |
| 37 |
| 38 ### Linux |
| 39 |
| 40 On Linux due to the sandbox we launch subprocesses by repeatedly forking from a |
| 41 helper process. This means that new subprocesses don't enter through main() |
| 42 again, but instead resume from clones in the middle of startup. The initial |
| 43 launch of the helper process still executes the normal startup path, so any |
| 44 initialization that happens in `ChromeMain()` will have been run for all |
| 45 subprocesses but they will all share the same initialization. |
OLD | NEW |