*: generalize "const trick"
While at it, change all "__asm__" to "asm"
Co-authored-by: canyie <31466456+canyie@users.noreply.github.com>
Signed-off-by: YU Jincheng <shana@zju.edu.cn>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/coreutils/test.c b/coreutils/test.c
index 7c65743..fc95672 100644
--- a/coreutils/test.c
+++ b/coreutils/test.c
@@ -435,7 +435,7 @@
};
/* See test_ptr_hack.c */
-extern struct test_statics *const test_ptr_to_statics;
+extern struct test_statics *BB_GLOBAL_CONST test_ptr_to_statics;
#define S (*test_ptr_to_statics)
#define args (S.args )
@@ -446,8 +446,7 @@
#define leaving (S.leaving )
#define INIT_S() do { \
- (*(struct test_statics**)not_const_pp(&test_ptr_to_statics)) = xzalloc(sizeof(S)); \
- barrier(); \
+ ASSIGN_CONST_PTR(test_ptr_to_statics, xzalloc(sizeof(S))); \
} while (0)
#define DEINIT_S() do { \
free(group_array); \
diff --git a/include/libbb.h b/include/libbb.h
index dfcaa05..02cc008 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -365,13 +365,27 @@
#endif
#endif
+/* We use a trick to have more optimized code (fewer pointer reloads
+ * and reduced binary size by a few kilobytes) like:
+ * ash.c: extern struct globals *const ash_ptr_to_globals;
+ * ash_ptr_hack.c: struct globals *ash_ptr_to_globals;
+ * This way, compiler in ash.c knows the pointer can not change.
+ *
+ * However, this may break on weird arches or toolchains. In this case,
+ * set "-DBB_GLOBAL_CONST=''" in CONFIG_EXTRA_CFLAGS to disable
+ * this optimization.
+ */
+#ifndef BB_GLOBAL_CONST
+# define BB_GLOBAL_CONST const
+#endif
+
#if defined(errno)
/* If errno is a define, assume it's "define errno (*__errno_location())"
* and we will cache it's result in this variable */
-extern int *const bb_errno;
-#undef errno
-#define errno (*bb_errno)
-#define bb_cached_errno_ptr 1
+extern int *BB_GLOBAL_CONST bb_errno;
+# undef errno
+# define errno (*bb_errno)
+# define bb_cached_errno_ptr 1
#endif
#if !(ULONG_MAX > 0xffffffff)
@@ -2270,6 +2284,8 @@
* If you want to assign a value, use SET_PTR_TO_GLOBALS(x) */
extern struct globals *const ptr_to_globals;
+#define barrier() asm volatile ("":::"memory")
+
#if defined(__clang_major__) && __clang_major__ >= 9
/* Clang/llvm drops assignment to "constant" storage. Silently.
* Needs serious convincing to not eliminate the store.
@@ -2277,7 +2293,7 @@
static ALWAYS_INLINE void* not_const_pp(const void *p)
{
void *pp;
- __asm__ __volatile__(
+ asm volatile (
"# forget that p points to const"
: /*outputs*/ "=r" (pp)
: /*inputs*/ "0" (p)
@@ -2288,13 +2304,13 @@
static ALWAYS_INLINE void* not_const_pp(const void *p) { return (void*)p; }
#endif
-/* At least gcc 3.4.6 on mipsel system needs optimization barrier */
-#define barrier() __asm__ __volatile__("":::"memory")
-#define SET_PTR_TO_GLOBALS(x) do { \
- (*(struct globals**)not_const_pp(&ptr_to_globals)) = (void*)(x); \
+#define ASSIGN_CONST_PTR(p, v) do { \
+ *(void**)not_const_pp(&p) = (void*)(v); \
+ /* At least gcc 3.4.6 on mipsel needs optimization barrier */ \
barrier(); \
} while (0)
+#define SET_PTR_TO_GLOBALS(x) ASSIGN_CONST_PTR(ptr_to_globals, x)
#define FREE_PTR_TO_GLOBALS() do { \
if (ENABLE_FEATURE_CLEAN_UP) { \
free(ptr_to_globals); \
diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 5c5d7eb..bf26c99 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -247,8 +247,7 @@
IF_FEATURE_INDIVIDUAL(, char **argv))
{
#ifdef bb_cached_errno_ptr
- (*(int **)not_const_pp(&bb_errno)) = get_perrno();
- barrier();
+ ASSIGN_CONST_PTR(bb_errno, get_perrno());
#endif
applet_name = applet;
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index a7a3ee1..3c87abc 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -192,7 +192,7 @@
};
/* See lineedit_ptr_hack.c */
-extern struct lineedit_statics *const lineedit_ptr_to_statics;
+extern struct lineedit_statics *BB_GLOBAL_CONST lineedit_ptr_to_statics;
#define S (*lineedit_ptr_to_statics)
#define state (S.state )
@@ -214,8 +214,7 @@
#define delbuf (S.delbuf )
#define INIT_S() do { \
- (*(struct lineedit_statics**)not_const_pp(&lineedit_ptr_to_statics)) = xzalloc(sizeof(S)); \
- barrier(); \
+ ASSIGN_CONST_PTR(lineedit_ptr_to_statics, xzalloc(sizeof(S))); \
} while (0)
static void deinit_S(void)
diff --git a/procps/powertop.c b/procps/powertop.c
index fc6018b..24c2b32 100644
--- a/procps/powertop.c
+++ b/procps/powertop.c
@@ -505,7 +505,7 @@
unsigned int *edx)
{
/* EAX value specifies what information to return */
- __asm__(
+ asm (
" pushl %%ebx\n" /* Save EBX */
" cpuid\n"
" movl %%ebx, %1\n" /* Save content of EBX */
diff --git a/shell/ash.c b/shell/ash.c
index 4bf0615..7b85981 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -303,20 +303,6 @@
# error "Do not even bother, ash will not run on NOMMU machine"
#endif
-/* We use a trick to have more optimized code (fewer pointer reloads):
- * ash.c: extern struct globals *const ash_ptr_to_globals;
- * ash_ptr_hack.c: struct globals *ash_ptr_to_globals;
- * This way, compiler in ash.c knows the pointer can not change.
- *
- * However, this may break on weird arches or toolchains. In this case,
- * set "-DBB_GLOBAL_CONST=''" in CONFIG_EXTRA_CFLAGS to disable
- * this optimization.
- */
-#ifndef BB_GLOBAL_CONST
-# define BB_GLOBAL_CONST const
-#endif
-
-
/* ============ Hash table sizes. Configurable. */
#define VTABSIZE 39
@@ -518,8 +504,7 @@
#define random_gen (G_misc.random_gen )
#define backgndpid (G_misc.backgndpid )
#define INIT_G_misc() do { \
- (*(struct globals_misc**)not_const_pp(&ash_ptr_to_globals_misc)) = xzalloc(sizeof(G_misc)); \
- barrier(); \
+ ASSIGN_CONST_PTR(ash_ptr_to_globals_misc, xzalloc(sizeof(G_misc))); \
savestatus = -1; \
curdir = nullstr; \
physdir = nullstr; \
@@ -1597,8 +1582,7 @@
#define g_stacknleft (G_memstack.g_stacknleft)
#define stackbase (G_memstack.stackbase )
#define INIT_G_memstack() do { \
- (*(struct globals_memstack**)not_const_pp(&ash_ptr_to_globals_memstack)) = xzalloc(sizeof(G_memstack)); \
- barrier(); \
+ ASSIGN_CONST_PTR(ash_ptr_to_globals_memstack, xzalloc(sizeof(G_memstack))); \
g_stackp = &stackbase; \
g_stacknxt = stackbase.space; \
g_stacknleft = MINSIZE; \
@@ -2229,8 +2213,7 @@
#endif
#define INIT_G_var() do { \
unsigned i; \
- (*(struct globals_var**)not_const_pp(&ash_ptr_to_globals_var)) = xzalloc(sizeof(G_var)); \
- barrier(); \
+ ASSIGN_CONST_PTR(ash_ptr_to_globals_var, xzalloc(sizeof(G_var))); \
for (i = 0; i < ARRAY_SIZE(varinit_data); i++) { \
varinit[i].flags = varinit_data[i].flags; \
varinit[i].var_text = varinit_data[i].var_text; \