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tools/nolibc: add alloca()

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Add the wide-used alloca() function. As it is highly machine and
compiler dependent, just defer to the compiler builtin. This has
been available since GCC 4 and clang 3.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260409-nolibc-alloca-v1-1-ed02f68dfaf9@weissschuh.net
This commit is contained in:
Thomas Weißschuh
2026-04-09 17:55:28 +02:00
parent f94da2b42b
commit 80e5de852e
4 changed files with 31 additions and 0 deletions
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1
tools/include/nolibc/Makefile
View File

@@ -20,6 +20,7 @@ OUTPUT ?= $(CURDIR)/
architectures := arm arm64 loongarch m68k mips powerpc riscv s390 sh sparc x86
arch_files := arch.h $(addsuffix .h, $(addprefix arch-, $(architectures)))
all_files := \
alloca.h \
assert.h \
byteswap.h \
compiler.h \

15
tools/include/nolibc/alloca.h Normal file
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@@ -0,0 +1,15 @@
/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
* alloca() for NOLIBC
* Copyright (C) 2026 Thomas Weißschuh <linux@weissschuh.net>
*/
/* make sure to include all global symbols */
#include "nolibc.h"
#ifndef _NOLIBC_ALLOCA_H
#define _NOLIBC_ALLOCA_H
#define alloca(size) __builtin_alloca(size)
#endif /* _NOLIBC_ALLOCA_H */

1
tools/include/nolibc/nolibc.h
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@@ -134,6 +134,7 @@
#include "byteswap.h"
#include "endian.h"
#include "assert.h"
#include "alloca.h"
/* Used by programs to avoid std includes */
#define NOLIBC

14
tools/testing/selftests/nolibc/nolibc-test.c
View File

@@ -45,6 +45,7 @@
#include <stdbool.h>
#include <byteswap.h>
#include <endian.h>
#include <alloca.h>
#pragma GCC diagnostic ignored "-Wmissing-prototypes"
@@ -1516,6 +1517,18 @@ int run_syscall(int min, int max)
return ret;
}
int test_alloca(void)
{
uint64_t *x;
x = alloca(sizeof(*x));
*x = 0x1234;
__asm__ ("" : "+r" (x));
return *x - 0x1234;
}
int test_difftime(void)
{
if (difftime(200., 100.) != 100.)
@@ -1731,6 +1744,7 @@ int run_stdlib(int min, int max)
CASE_TEST(toupper_noop); EXPECT_EQ(1, toupper('A'), 'A'); break;
CASE_TEST(abs); EXPECT_EQ(1, abs(-10), 10); break;
CASE_TEST(abs_noop); EXPECT_EQ(1, abs(10), 10); break;
CASE_TEST(alloca); EXPECT_ZR(1, test_alloca()); break;
CASE_TEST(difftime); EXPECT_ZR(1, test_difftime()); break;
CASE_TEST(memchr_foobar6_o); EXPECT_STREQ(1, memchr("foobar", 'o', 6), "oobar"); break;
CASE_TEST(memchr_foobar3_b); EXPECT_STRZR(1, memchr("foobar", 'b', 3)); break;