FORTIFY_SOURCE: optimize
Don't do the fortify_source checks if we can determine, at
compile time, that the provided operation is safe.
This avoids silliness like calling fortify source on things like:
size_t len = strlen("asdf");
printf("%d\n", len);
and allows the compiler to optimize this code to:
printf("%d\n", 4);
Defer to gcc's builtin functions instead of pointing our code
to the libc implementation.
Change-Id: I5e1dcb61946461c4afaaaa983e39f07c7a0df0ae
diff --git a/libc/include/string.h b/libc/include/string.h
index 6643d28..70e0042 100644
--- a/libc/include/string.h
+++ b/libc/include/string.h
@@ -201,8 +201,6 @@
return __strlcat_chk(dest, src, size, bos);
}
-__purefunc extern size_t __strlen_real(const char *)
- __asm__(__USER_LABEL_PREFIX__ "strlen");
extern size_t __strlen_chk(const char *, size_t);
__BIONIC_FORTIFY_INLINE
@@ -211,14 +209,17 @@
// Compiler doesn't know destination size. Don't call __strlen_chk
if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
- return __strlen_real(s);
+ return __builtin_strlen(s);
+ }
+
+ size_t slen = __builtin_strlen(s);
+ if (__builtin_constant_p(slen)) {
+ return slen;
}
return __strlen_chk(s, bos);
}
-__purefunc extern char* __strchr_real(const char *, int)
- __asm__(__USER_LABEL_PREFIX__ "strchr");
extern char* __strchr_chk(const char *, int, size_t);
__BIONIC_FORTIFY_INLINE
@@ -227,14 +228,17 @@
// Compiler doesn't know destination size. Don't call __strchr_chk
if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
- return __strchr_real(s, c);
+ return __builtin_strchr(s, c);
+ }
+
+ size_t slen = __builtin_strlen(s);
+ if (__builtin_constant_p(slen) && (slen < bos)) {
+ return __builtin_strchr(s, c);
}
return __strchr_chk(s, c, bos);
}
-__purefunc extern char* __strrchr_real(const char *, int)
- __asm__(__USER_LABEL_PREFIX__ "strrchr");
extern char* __strrchr_chk(const char *, int, size_t);
__BIONIC_FORTIFY_INLINE
@@ -243,7 +247,12 @@
// Compiler doesn't know destination size. Don't call __strrchr_chk
if (bos == __BIONIC_FORTIFY_UNKNOWN_SIZE) {
- return __strrchr_real(s, c);
+ return __builtin_strrchr(s, c);
+ }
+
+ size_t slen = __builtin_strlen(s);
+ if (__builtin_constant_p(slen) && (slen < bos)) {
+ return __builtin_strrchr(s, c);
}
return __strrchr_chk(s, c, bos);