Document CCACHE_BASEDIR

diff --git a/NEWS b/NEWS
index 0a9884a79ae5cf29091f5b0579b9920ba4cde782..c44fa9278fc619e4f1f4f26fa5517c2355f03db2 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -10,13 +10,14 @@ New features and improvements:
     speedup will be higher when I/O is fast (e.g., when files are in the disk
     cache). The direct mode can be disabled by setting CCACHE_NODIRECT.
 
-  - When hashing the output from the preprocessor, absolute paths for which the
-    path specified by CCACHE_BASEDIR is a prefix are rewritten to relative.
-    Paths specified by -I and similar flags get the same treatment. This is
-    done to get cache hits even when compiling with -g and when using absolute
-    include directory paths. Absolute paths in the standard error text will
-    also be more accurate. CCACHE_BASEDIR defaults to the current working
-    directory.
+  - When hashing the output from the preprocessor, absolute paths are rewritten
+    to relative paths, but only for paths under the directory specified by
+    CCACHE_BASEDIR. Paths specified by -I and similar options get the same
+    treatment. This is done to get cache hits even when compiling with -g and
+    when using absolute include directory paths. Absolute paths in the standard
+    error text will also be more accurate. The default value of CCACHE_BASEDIR
+    is the current working directory. To disable the rewriting, set
+    CCACHE_BASEDIR to the empty string.
 
   - Object files are now by default stored compressed in the cache. The runtime
     cost is negligible, and more files will fit in the ccache directory and in

diff --git a/ccache.yo b/ccache.yo
index 151c4677ceeeab0b2abc17d1b1fb2ead226be3b1..21704e0a65b3331cf5a3f4e629339868eb7aba01 100644 (file)
--- a/ccache.yo
+++ b/ccache.yo
@@ -124,6 +124,15 @@ most cases you won't need any of these as the defaults will be fine.
 
 startdit()
 
+dit(bf(CCACHE_BASEDIR)) When hashing the output from the preprocessor,
+absolute paths are rewritten to relative paths, but only for paths
+under the directory specified by CCACHE_BASEDIR. Paths specified by -I
+and similar options get the same treatment. This is done to get cache
+hits even when compiling with -g and when using absolute include
+directory paths. The default value of CCACHE_BASEDIR is the current
+working directory. To disable the rewriting, set CCACHE_BASEDIR to the
+empty string.
+
 dit(bf(CCACHE_CC)) You can optionally set CCACHE_CC to force the name
 of the compiler to use. If you don't do this then ccache works it out
 from the command line.