The /verbose:incr switch will print various diagnostic messages you can use to determine when the linker had to abandon incremental linking and fall back to a full link. There are two switches you can use to get diagnostic information about the incremental linking process. Note also, that /INCREMENTAL is implied if you have specified /DEBUG. The /INCREMENTAL switch is off by default for the Release and Profile configurations. INCREMENTAL is on by default in the Debug configuration for projects created using Visual Studio. If you’re building from within Visual Studio, /INCREMENTAL can be turned on using the Enable Incremental Linking property: Incremental linking is turned on by passing the /INCREMENTAL switch on the linker command line. The remainder of this section describes the set of switches you’ll use to turn on incremental linking and provides a set of guidelines to maximize the chance that incremental linking will succeed. However, larger binaries will take longer to deploy on remote hosts so you’ll want to verify whether this tradeoff is acceptable in your particular scenario.Įven if the linker is properly configured to link incrementally, sadly today there are several factors that will force the linker to fall back and do a full link (we are working on improving this). In the developer iteration scenario, the additional size is generally accepted as a fair tradeoff for faster link times. As a result, a binary built with incremental linking enabled will be larger than a binary built without incremental linking. To enable the ability to add code to an existing binary on subsequent links, the linker inserts extra padding into a binary as it’s being built. In addition to incrementally updating the binary, the linker incrementally updates the corresponding PDB as well. This approach is much faster because the linker is only updating the part of the existing binary that was impacted by the code changes rather than having to recreate the binary from its constituent objects and libraries from the ground up. When linking incrementally, the linker directly updates the binaries produced on the previous link rather than building them from scratch. The key to optimal linker performance in the developer iteration scenario is to link the application incrementally. I will be covering this over a couple of blogs, with this particular one covering the developer iteration scenario in some detail. This blog describes a set of best practices that will enable you to get the most out of the Visual C++ linker both when iterating during development and while producing a final release build. These two scenarios require the linker to be configured quite differently. In this scenario, the amount of time it takes the link to finish is secondary to ensuring that an optimal binary is produced, both from the perspective of size and performance. The other scenario to consider is producing a final build in preparation for release. Developers are often willing to trade off executable size and code quality in order to reduce iteration times. In this scenario, the primary objective is to make the cycle from a code change to seeing that change running on the console as quick as possible. The first is the developer iteration scenario. There are essentially two primary scenarios to consider when looking at link time. The ‘Final: Total time’ reports the total time spent in the link phase. A user can quickly determine this by adding the ‘/time’ flag to the linker command line. If you also need to enable remote to local link evaluation, you can substitute R2R:1 with R2L:1 in the set behavior command.The time spent in the link phase could be a significant portion of an applications overall build time for most large projects. Remote to remote symbolic links are enabled. To check that the setting has been updated, enter the evaluation query again: C:\>fsutil behavior query SymlinkEvaluation You won't see any response if the command was successful. In order to enable remote to remote symbolic links, enter the following command: C:\>fsutil behavior set SymlinkEvaluation R2R:1 Remote to remote symbolic links are disabled. You'll notice the last line of the response to the above command notes that Remote to local symbolic links are disabled. Local to remote symbolic links are enabled. Local to local symbolic links are enabled. To view the current status of the Symlink settings on your system, execute the following command from an elevated (administrator) command prompt:įsutil behavior query SymlinkEvaluation C:\>fsutil behavior query SymlinkEvaluation This is because by default remote to remote symbolic links are disabled. The symbolic link cannot be followed because its type is disabled Occasionally, when copying folders from remote servers, or when accessing a symbolic link directly on a file server, you may see the following error:
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