Add a comment re VG_(expand_file_name).

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@8773

diff --git a/include/pub_tool_options.h b/include/pub_tool_options.h
index 0183f1d0b70c8ab895696834eb919c7aa6098ff8..7d8e60f6a06a9b0e2ec81d4c8057a203a7c297d9 100644 (file)
--- a/include/pub_tool_options.h
+++ b/include/pub_tool_options.h
@@ -127,7 +127,7 @@ extern Int   VG_(clo_backtrace_size);
 __attribute__((noreturn))
 extern void VG_(err_bad_option) ( Char* opt );
 
-/* Used to expand file names.  'option_name" is the option name, eg.
+/* Used to expand file names.  "option_name" is the option name, eg.
    "--log-file".  'format' is what follows, eg. "cachegrind.out.%p".  In
    'format': 
    - "%p" is replaced with PID.
@@ -138,6 +138,12 @@ extern void VG_(err_bad_option) ( Char* opt );
    If the format specifies a relative file name, it's put in the program's
    initial working directory.  If it specifies an absolute file name (ie.
    starts with '/') then it is put there.
+
+   Note that "option_name" has no effect on the returned string: the
+   returned string depends only on "format" and the PIDs and
+   environment variables that it references (if any). "option_name" is
+   merely used in printing error messages, if an error message needs
+   to be printed due to malformedness of the "format" argument.
 */
 extern Char* VG_(expand_file_name)(Char* option_name, Char* format);