[PATCH] libbb: reduce reliance on -funsigned-char

[Daniel Dadap]

The default CFLAGS assigned by the build system include -funsigned-char,
so that certain arithmetic operations on buffer contents can behave as
expected. However, when setting CFLAGS on the make command line, these
defaults get overridden, and if one neglects to include -funsigned-char
in the override CFLAGS, some applets such as `sum` may produce results
which are incorrect.

Update the declaration of the bb_common_bufsiz1 buffer, which is used by
`sum` and others, to explicitly make it a buffer of unsigned char. This
should be harmless, since this is the case anyway with -funsigned-char.
Several other pointers, which are used to do pointer arithmetic against
bb_common_bufsiz1, are also updated to be declared unsigned char.

With this change, `sum` now produces correct results regardless of the
presence of the -funsigned-char CFLAG. However, since there may still be
other implicit dependencies on unsigned char behavior, -funsigned-char
remains in the default CFLAGS assignment.

Signed-off-by: Daniel Dadap <ddadap at nvidia.com>
---
 libbb/common_bufsiz.c      | 6 +++---
 miscutils/fbsplash.c       | 2 +-
 miscutils/tree.c           | 2 +-
 procps/nmeter.c            | 4 ++--
 scripts/generate_BUFSIZ.sh | 4 ++--
 5 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/libbb/common_bufsiz.c b/libbb/common_bufsiz.c
index 6bc6d7bc9..d7577fa9d 100644
--- a/libbb/common_bufsiz.c
+++ b/libbb/common_bufsiz.c
@@ -50,7 +50,7 @@
 /* We use it for "global" data via *(struct global*)bb_common_bufsiz1.
  * Since gcc insists on aligning struct global's members, it would be a pity
  * (and an alignment fault on some CPUs) to mess it up. */
-char bb_common_bufsiz1[COMMON_BUFSIZE] ALIGNED(sizeof(long long));
+unsigned char bb_common_bufsiz1[COMMON_BUFSIZE] ALIGNED(sizeof(long long));
 
 #else
 
@@ -68,7 +68,7 @@ char bb_common_bufsiz1[COMMON_BUFSIZE] ALIGNED(sizeof(long long));
  * It is not defined as a dummy macro.
  * It means we have to provide this function.
  */
-char *const bb_common_bufsiz1 __attribute__ ((section (".data")));
+unsigned char *const bb_common_bufsiz1 __attribute__ ((section (".data")));
 void setup_common_bufsiz(void)
 {
 	if (!bb_common_bufsiz1)
@@ -77,7 +77,7 @@ void setup_common_bufsiz(void)
 # else
 #  ifndef bb_common_bufsiz1
    /* bb_common_bufsiz1[] is not aliased to _end[] */
-char bb_common_bufsiz1[COMMON_BUFSIZE] ALIGNED(sizeof(long long));
+unsigned char bb_common_bufsiz1[COMMON_BUFSIZE] ALIGNED(sizeof(long long));
 #  endif
 # endif
 
diff --git a/miscutils/fbsplash.c b/miscutils/fbsplash.c
index 2934d8eb7..576546f5f 100644
--- a/miscutils/fbsplash.c
+++ b/miscutils/fbsplash.c
@@ -375,7 +375,7 @@ static void fb_drawprogressbar(unsigned percent)
 static void fb_drawimage(void)
 {
 	FILE *theme_file;
-	char *read_ptr;
+	unsigned char *read_ptr;
 	unsigned char *pixline;
 	unsigned i, j, width, height, line_size;
 
diff --git a/miscutils/tree.c b/miscutils/tree.c
index 0b142c85c..3b58edc04 100644
--- a/miscutils/tree.c
+++ b/miscutils/tree.c
@@ -23,7 +23,7 @@
 
 #define prefix_buf bb_common_bufsiz1
 
-static void tree_print(unsigned count[2], const char* directory_name, char* prefix_pos)
+static void tree_print(unsigned count[2], const char* directory_name, unsigned char* prefix_pos)
 {
 	struct dirent **entries;
 	int index, size;
diff --git a/procps/nmeter.c b/procps/nmeter.c
index dca07eac6..edce265ea 100644
--- a/procps/nmeter.c
+++ b/procps/nmeter.c
@@ -87,7 +87,7 @@ struct globals {
 	// 1 if sample delay is not an integer fraction of a second
 	smallint need_seconds;
 	char final_char;
-	char *cur_outbuf;
+	unsigned char *cur_outbuf;
 	int delta;
 	unsigned deltanz;
 	struct timeval tv;
@@ -136,7 +136,7 @@ static void print_outbuf(void)
 
 static void put(const char *s)
 {
-	char *p = cur_outbuf;
+	unsigned char *p = cur_outbuf;
 	int sz = outbuf + COMMON_BUFSIZE - p;
 	while (*s && --sz >= 0)
 		*p++ = *s++;
diff --git a/scripts/generate_BUFSIZ.sh b/scripts/generate_BUFSIZ.sh
index 718788e0b..fae7d68a7 100755
--- a/scripts/generate_BUFSIZ.sh
+++ b/scripts/generate_BUFSIZ.sh
@@ -28,7 +28,7 @@ generate_std_and_exit() {
 	$debug && echo "Configuring: bb_common_bufsiz1[] in bss"
 	{
 	echo "enum { COMMON_BUFSIZE = 1024 };"
-	echo "extern char bb_common_bufsiz1[];"
+	echo "extern unsigned char bb_common_bufsiz1[];"
 	echo "#define setup_common_bufsiz() ((void)0)"
 	} | regenerate "$common_bufsiz_h"
 	echo "std" >"$common_bufsiz_h.method"
@@ -39,7 +39,7 @@ generate_big_and_exit() {
 	$debug && echo "Configuring: bb_common_bufsiz1[] in bss, COMMON_BUFSIZE = $1"
 	{
 	echo "enum { COMMON_BUFSIZE = $1 };"
-	echo "extern char bb_common_bufsiz1[];"
+	echo "extern unsigned char bb_common_bufsiz1[];"
 	echo "#define setup_common_bufsiz() ((void)0)"
 	} | regenerate "$common_bufsiz_h"
 	echo "$2" >"$common_bufsiz_h.method"
-- 
2.39.5