Ensure variable_buffer is always set.

Initialize the global variable_buffer in main() so that it is never
a null pointer.  Then invoking variable_expand("") is never needed:
simply use the variable_buffer pointer when we want to restart the
variable buffer.  The main point of this simplification is not to
keep a separate pointer to the beginning of the buffer: this is
dangerous because the buffer may be re-allocated.  Instead always
use the variable_buffer pointer itself.

* src/variable.h (initialize_variable_output): Publish.
* src/expand.c (initialize_variable_output): Remove static.
* src/main.c (main): Initialize variable_buffer.
* src/file.c (enter_prereqs): Don't call variable_expand("") and
don't save a separate buffer pointer than might be outdated.
(expand_deps): Ditto.
* src/read.c (record_files): Ditto.
* src/remake.c (library_search): Ditto.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/expand.c b/src/expand.c
index 0b6bb255..6e5d6d85 100644
--- a/src/expand.c
+++ b/src/expand.c
@@ -71,10 +71,11 @@ variable_buffer_output (char *ptr, const char *string, size_t length)
   return ptr + length;
 }
 
-/* Return a pointer to the beginning of the variable buffer.  */
+/* Return a pointer to the beginning of the variable buffer.
+   This is called from main() and it should never be null afterward.  */
 
-static char *
-initialize_variable_output (void)
+char *
+initialize_variable_output ()
 {
   /* If we don't have a variable output buffer yet, get one.  */
 
@@ -207,7 +208,7 @@ variable_expand_string (char *line, const char *string, size_t length)
   if (length == 0)
     {
       variable_buffer_output (o, "", 1);
-      return (variable_buffer);
+      return variable_buffer;
     }
 
   /* We need a copy of STRING: due to eval, it's possible that it will get