[OvOhao]

What changed

include/wayinfo.h (#59): BUF now expands to buf + strlen(buf), sizeof(buf) - strlen(buf), and all 20 sprintf(BUF, ...) calls are now snprintf(BUF, ...). Every append is limited to the space left in buf; output that does not fit is truncated instead of being written past the end of the 10240 byte buffer. The output for anything that fits is unchanged.

xinfo.go (#60), wayinfo.go (#61): X11InfoString() / WaylandInfoString() return a calloc'ed copy of the info text and clear the static buffer, so the caller owns the returned pointer. XInfo() and WaylandInfo() now keep the pointer, copy it with C.GoString and C.free it (deferred). Both headers already include <stdlib.h>. C.free(NULL) and C.GoString(nil) are both safe, so a NULL return still produces an empty string as before.

Testing

Run in a golang:1.27 (Debian, arm64) container with libx11-dev libxcursor-dev libxmu-dev libwayland-dev libxpm-dev xbitmaps libxmu-headers libheif-dev (the CI package list), plus Xvfb :99 -noreset with two screens and weston --backend=headless:

• make succeeds and go vet . passes, before and after.
• go test -count=10 -mod=vendor -run 'TestXMonitors|TestWaylandMonitors' -v .: 10/10 passes for each test, before and after. Both return the same monitors as before.
• A small C program built with -fsanitize=address that includes include/wayinfo.h and passes sprint_infos() 100 registry entries with 200 character interface names:
  • before: AddressSanitizer: global-buffer-overflow ... WRITE of size 237 in vsprintf
  • after: no error, strlen(buf) = 10239, sizeof(buf) = 10240
• A local loop of 20,000 calls measuring the C heap in use (mallinfo2().uordblks):

Call	before	after
XInfo() (281 byte result)	+304 bytes/call	+0 bytes/call
WaylandInfo() (1339 byte result)	+3619 bytes/call	+2258 bytes/call

The remaining growth in WaylandInfo() comes from the per-call registry/output records in wayinfo.h. This PR does not change them.

Fixes #59
Fixes #60
Fixes #61

[xyproto]

Thanks for the PR, merged.