Errors frequently occur when debugging portfile.cmake

I noticed that the following errors will occur when debugging some port's portfile:

/Users/jackyu/Documents/vcpkg/installed/vcpkg/vcpkg-running.lock: note: waiting to take filesystem lock... 
/Users/jackyu/Documents/vcpkg/installed/vcpkg/vcpkg-running.lock: note: waiting to take filesystem lock... 
/Users/jackyu/Documents/vcpkg/installed/vcpkg/vcpkg-running.lock: note: waiting to take filesystem lock... 
/Users/jackyu/Documents/vcpkg/installed/vcpkg/vcpkg-running.lock: error: calling try_take_exclusive_file_lock failed with 16 (Resource busy) 
/Users/jackyu/Documents/vcpkg/installed/vcpkg/vcpkg-running.lock: error: failed to take lock, another vcpkg may be running against the same directory

Example command:

rm -f /tmp/vcpkg_ext_portfile_dbg /tmp/vscode-vcpkg-cmakelists-debugger-pipe && "/Users/jackyu/Documents/vcpkg/vcpkg" remove cpp-httplib --recurse && "/Users/jackyu/Documents/vcpkg/vcpkg" install "cpp-httplib[zlib]"  --editable --no-binarycaching --x-cmake-debug /tmp/vcpkg_ext_portfile_dbg --x-cmake-configure-debug /tmp/vscode-vcpkg-cmakelists-debugger-pipe 

Analysis from AI:

Root Cause Analysis

In vcpkg-tool, the vcpkg-running.lock error was caused by:

  1. Extremely Short Retry Timeout in try_take_exclusive_file_lock (only 1.4s): In src/vcpkg/base/files.cpp, the retry backoff was:
    • 1st retry: wait 200 ms
    • 2nd retry: wait 400 ms
    • 3rd retry: wait 800 ms
    • Once total wait exceeded 1.4 seconds (1400 ms), it immediately failed with EBUSY (Resource busy) and exited the process.
  2. Concurrency / Race Conditions in IDE Environments: When chained commands (e.g., vcpkg remove ... && vcpkg install ...) or background IDE tasks (such as tree view dependency queries) run in quick succession, the previous process might take a few hundred milliseconds to fully release the kernel file descriptor lock. With a 1.4s threshold, vcpkg would frequently fail with error: calling try_take_exclusive_file_lock failed with 16 (Resource busy).

Changes Implemented in vcpkg-tool (/Users/jackyu/Documents/vcpkg-tool)

  1. Extended Retry Timeout with Smooth Exponential Backoff (src/vcpkg/base/files.cpp):
    • Increased the total wait duration in try_take_exclusive_file_lock from 1.4s to 30 seconds (30000 ms).
    • Implemented exponential backoff with a 1-second interval cap (200ms $\to$ 400ms $\to$ 800ms $\to$ 1000ms $\dots$). As soon as the preceding process releases the lock, the waiting command immediately acquires it and proceeds smoothly.
  2. Added Environment Variable Support for X_VCPKG_WAIT_FOR_LOCK:
    • Declared EnvironmentVariableXVcpkgWaitForLock = "X_VCPKG_WAIT_FOR_LOCK" in include/vcpkg/base/contractual-constants.h.
    • Handled the environment variable in src/vcpkg/vcpkgcmdarguments.cpp so that X_VCPKG_WAIT_FOR_LOCK=1 globally enables blocking lock acquisition (wait_for_lock = true).

Fix from AI:
fix_lock_exist.diff.zip

I tried the fix and it works fine. And I checked the changes, looks good to me.

Start with src/vcpkg/base/files.cpp and reproduce the lock failure using the example vcpkg remove/install command with debugging enabled. Review include/vcpkg/base/contractual-constants.h and src/vcpkg/vcpkgcmdarguments.cpp for the proposed X_VCPKG_WAIT_FOR_LOCK handling; done means debugging no longer fails during the reported lock race and the relevant behavior is verified.