Messages in this thread Patch in this message | | | From | Willy Tarreau <> | Subject | [PATCH 05/22] tools/nolibc: make errno a weak symbol instead of a static one | Date | Mon, 9 Jan 2023 09:41:51 +0100 |
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Till now errno was declared static so that it could be eliminated if unused. While the goal is commendable for tiny executables as it allows to eliminate any data and bss segments when not used, this comes with some limitations, one of which being that the errno symbol seen in different units are not the same. Even though this has never been a real issue given the nature of the programs involved till now, it happens that referencing the same symbol from multiple units can also be achieved using weak symbols, with a difference being that only one of them will be used for all of them. Compared to weak symbols, static basically have no benefit for regular programs since there are always at least a few variables in most of these, so the bss segment cannot be eliminated. E.g:
$ size nolibc-test-static-errno text data bss dec hex filename 11531 0 48 11579 2d3b nolibc-test-static-errno
Furthermore, the weak symbol doesn't use bss storage at all, resulting in a slightly section:
$ size nolibc-test-weak-errno text data bss dec hex filename 11531 0 40 11571 2d33 nolibc-test-weak-errno
This patch thus converts errno from static to weak.
Signed-off-by: Willy Tarreau <w@1wt.eu> --- tools/include/nolibc/errno.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/tools/include/nolibc/errno.h b/tools/include/nolibc/errno.h index 9dc4919c769b..a44486ff0477 100644 --- a/tools/include/nolibc/errno.h +++ b/tools/include/nolibc/errno.h @@ -9,11 +9,9 @@ #include <asm/errno.h> -/* this way it will be removed if unused */ -static int errno; - #ifndef NOLIBC_IGNORE_ERRNO #define SET_ERRNO(v) do { errno = (v); } while (0) +int errno __attribute__((weak)); #else #define SET_ERRNO(v) do { } while (0) #endif -- 2.17.5
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