[dev] [sbase][PATCH 2/2] Remove bit fields

From: Roberto E. Vargas Caballero <k0ga_AT_shike2.com>
Date: Fri, 20 Feb 2015 14:38:52 +0100

Before removing bit fields:

$ size find

   text data bss dec hex filename

  16751 968 48 17767 4567 find

After removing bit fields:
$ size find
   text data bss dec hex filename
  16527 968 68 17563 449b find

This is an example where bit fields uses more memory
than integers or char. There is going to be only one
gflags struct, so the waste in instructions is bigger
than the space saved by bit fields. In the case of Permarg,
Sizearg, Execarg there is only one bit field, so at least
one unsigned is used, so there is no any gain.

---
 find.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/find.c b/find.c
index 0043b95..d2d577b 100644
--- a/find.c
+++ b/find.c
_AT_@ -64,7 +64,7 @@ struct Tok {
 /* structures used for Arg.extra.p and Tok.extra.p */
 typedef struct {
 	mode_t        mode;
-	unsigned int  exact:1;
+	unsigned char exact;
 } Permarg;
 
 typedef struct {
_AT_@ -83,7 +83,7 @@ typedef struct {
 
 typedef struct {
 	Narg n;
-	unsigned int bytes:1; /* size is in bytes, not 512 byte sectors */
+	unsigned char bytes; /* size is in bytes, not 512 byte sectors */
 } Sizearg;
 
 typedef struct {
_AT_@ -100,7 +100,7 @@ typedef struct {
 		} p; /* plus */
 	} u;
 	char        **argv; /* NULL terminated list of arguments (allocated if isplus) */
-	unsigned int isplus:1; /* -exec + instead of -exec ; */
+	unsigned char isplus; /* -exec + instead of -exec ; */
 } Execarg;
 
 /* used to find loops while recursing through directory structure */
_AT_@ -221,14 +221,14 @@ size_t envlen; /* number of bytes in environ, used to calculate against ARG_MAX
 size_t argmax; /* value of ARG_MAX retrieved using sysconf(3p) */
 
 struct {
-	unsigned ret  :1; /* return value from main                                  */
-	unsigned depth:1; /* -depth, directory contents before directory itself      */
-	unsigned h    :1; /* -H, follow symlinks on command line                     */
-	unsigned l    :1; /* -L, follow all symlinks (command line and search)       */
-	unsigned prune:1; /* hit -prune, eval should return STW_PRUNE (return values
+	unsigned ret  ; /* return value from main                                  */
+	unsigned depth; /* -depth, directory contents before directory itself      */
+	unsigned h    ; /* -H, follow symlinks on command line                     */
+	unsigned l    ; /* -L, follow all symlinks (command line and search)       */
+	unsigned prune; /* hit -prune, eval should return STW_PRUNE (return values
 						 traversing expression tree are boolean so we can't
 						 easily return this. instead set a global flag)          */
-	unsigned xdev :1; /* -xdev, prune directories on different devices           */
+	unsigned xdev ; /* -xdev, prune directories on different devices           */
 } gflags;
 
 /*
-- 
2.1.2.532.g19b5d50

Received on Fri Feb 20 2015 - 14:38:52 CET