[wan9chi]

Motivation

The fexecve interposer (Linux) built /proc/self/fd/{fd} with format!, which goes through libc malloc. Exec may run in the child of fork(), where malloc's lock may be held by a thread that no longer exists, so the exec interposers avoid libc's heap.

Change

Format the path into a stack buffer with the existing proc_fd_path helper from fspy_client_unix::convert, now public. It takes the raw descriptor instead of a BorrowedFd, so -1 still formats as /proc/self/fd/-1 and the real execve reports the error as before.

🤖 Generated with Claude Code

[github-actions]

fspy benchmark

linux

dynamic/launch             change  +0.47%  [ -3.92% ..  +4.98%]  overhead   +54.84%
dynamic/access             change  -1.17%  [-16.21% ..  +2.66%]  overhead   +23.79%
dynamic/access-relative    change  -1.64%  [ -5.00% ..  +1.08%]  overhead   +68.96%
dynamic/access-contended   change  +1.58%  [ -9.79% ..  +8.27%]  overhead    +7.27%
static/launch              change  +0.79%  [ -4.59% ..  +6.36%]  overhead  +194.00%
static/access              change  +0.09%  [ -4.95% ..  +1.95%]  overhead +1364.76%
static/access-relative     change  -0.21%  [ -1.92% ..  +1.23%]  overhead +1855.77%
static/access-contended    change  +0.10%  [ -0.83% ..  +1.12%]  overhead +2020.13%

macos

dynamic/launch             change  +0.11%  [ -3.89% ..  +4.17%]  overhead  +229.11%
dynamic/access             change  -0.70%  [ -3.03% ..  +2.08%]  overhead    +1.70%
dynamic/access-relative    change  -0.43%  [ -5.38% ..  +3.84%]  overhead  +255.46%
dynamic/access-contended   change  -0.99%  [ -4.99% ..  +4.63%]  overhead    +1.66%

windows

dynamic/launch             change  +0.34%  [ -6.72% ..  +7.91%]  overhead   +25.08%
dynamic/access             change  +0.17%  [-11.32% .. +15.71%]  overhead    +1.92%
dynamic/access-relative    change  -0.13%  [-12.35% .. +10.89%]  overhead    +0.25%
dynamic/access-contended   change  +1.72%  [-14.63% .. +13.08%]  overhead    +4.20%