portconfigure: sync CCACHE_DIR env before exec ccache -M

[eejd]

Problem

macports.tcl sets env(CCACHE_DIR) once at startup to the global ccache_dir default ($portdbpath/build/.ccache, typically /opt/local/var/macports/build/.ccache).

A Portfile can override the Tcl variable ccache_dir to a per-build workpath — py-pytorch does this:

set ccache_dir ${workpath}/.ccache

portconfigure.tcl (configure_start) correctly picks up the overridden Tcl variable and creates/chowns that per-build directory. However the subsequent exec ccache -M ${ccache_size} inherits the stale process-level CCACHE_DIR that still points at the never-created, root-owned default path. The result is:

Warning: ccache_dir .../work/.ccache could not be initialized; disabling ccache:
ccache: error: Failed to create directory .../build/.ccache: Permission denied

ccache is silently disabled for the entire build even though the port set things up correctly.

Root cause

portconfigure.tcl lines 423–431 (excerpt):

# Initialize ccache directory with the given maximum size
if {${configure.ccache}} {
    if {[catch {
        exec ccache -M ${ccache_size} >/dev/null   ;# ← uses env(CCACHE_DIR), not ${ccache_dir}
    } result]} {
        ui_warn "ccache_dir ${ccache_dir} could not be initialized; disabling ccache: $result"

env(CCACHE_DIR) is never updated to match the current (possibly overridden) ${ccache_dir} before exec ccache runs.

Fix

One line added immediately before the exec:

set env(CCACHE_DIR) ${ccache_dir}

This syncs the environment to whatever ccache_dir was resolved to (global default or per-build override) so the ccache -M call targets the directory that was just prepared with file mkdir / file attributes.

Verification

Reproduced on MacPorts 2.12.5, ccache 4.13.1, macOS 26 (Darwin 25.5.0) with py314-pytorch. Applying the patch and rebuilding eliminates the warning and ccache works correctly for the build.

Workaround (until this lands)

sudo mkdir /opt/local/var/macports/build/.ccache
sudo chown macports:macports /opt/local/var/macports/build/.ccache

This is fragile — the directory is wiped by sudo port clean --all.

[jmroot]

Globals representing macports.conf values are not meant to be modified, so what py-pytorch is doing is not supported. We might start defining them as const now that we're adopting Tcl 9 which allows that. If we want to allow changing the ccache dir (and I don't know if we do), there should be a new option which takes its default value from the existing ccache_dir.

[eejd]

Thanks — that's a fair objection, and it makes this patch the wrong shape.

Syncing env(CCACHE_DIR) to the resolved ${ccache_dir} fixes the mechanism, but it also legitimises a port assigning to a macports.conf-backed global, which is exactly what you're saying isn't supported. Papering over that in configure_start isn't an improvement over const making it a hard error.

Withdrawing rather than leaving it open. If there's later appetite for a real configure.ccache_dir option defaulting to the global — the shape you described — that's a different change and worth proposing on the list first. The underlying py-pytorch behaviour is arguably a port bug in the meantime.