tree 6c1841e83d5288941463e080f447b2ed845d8969
parent ac0fe07d9e924661c6c443f4a9503d4f4308fb20
author John Drouhard <john@jmdtech.org> 1584302214 -0500
committer John Drouhard <john@jmdtech.org> 1615937971 -0500

Change build log to always log the most recent input mtime

If an edge's output files' mtimes are compared to the most recent
input's mtime, edges might be calculated as clean even if they are
actually dirty. While an edge's command is running its rule to produce
its outputs and an input to the edge is updated before the outputs are
written to disk, then subsequent runs will think that the outputs are
newer than the inputs, even though the inputs have actually been updated
and may be different than what were used to produce those outputs.

Ninja will now restat all inputs just prior to running an edge's command
and remember the most recent input mtime. When the command completes,
it will stat any discovered dependencies from dep files (if necessary),
recalculate the most recent input mtime, and log it to the build log
file. On subsequent runs, ninja will use this value to compare to the
edge's most recent input's mtime to determine whether the outputs are
dirty.

This extends the methodology used by restat rules to work in all cases.
Restat rules are still unique in that they will clean the edge's output
nodes recursively if the edge's command did not change the output, but
in all cases, the mtime recorded in the log file is now the most recent
input mtime. See the new tests for more clarification.