【发布时间】：2016-08-23 02:38:27
【问题描述】：
我正在编写一个与英特尔 DPDK 接口的 Rust 程序，但我遇到了一个我不太了解的问题。我目前可以在 Rust 程序中执行 DPDK 库中的函数，但它与用 C 编写的同一程序的结果不同。
Rust 程序输出 -
~/Dev/rust_eal_init_test$ sudo target/debug/rust_eal_init_test
EAL: Detected 8 lcore(s)
EAL: No free hugepages reported in hugepages-2048kB
EAL: Probing VFIO support...
~/Dev/rust_eal_init_test$
C 程序输出 -
~/Dev/c_eal_init_test$ sudo build/c_eal_init_test
EAL: Detected 8 lcore(s)
EAL: No free hugepages reported in hugepages-2048kB
EAL: Probing VFIO support...
PMD: bnxt_rte_pmd_init() called for (null)
EAL: PCI device 0000:00:19.0 on NUMA socket -1
EAL: probe driver: 8086:153a rte_em_pmd
EAL: PCI device 0000:04:00.0 on NUMA socket -1
EAL: probe driver: 8086:1533 rte_igb_pmd
~/Dev/c_eal_init_test$
DPDK 已编译为我在 Rust 中链接到的静态库。下面是 Rust 和 C 程序的代码。
Rust main.rs -
extern crate libc;
use std::env;
use std::process::exit;
use std::ffi::CString;
use libc::{c_int, c_char,};
extern {
pub fn rte_eal_init(argc: c_int, argv: *mut *mut c_char) -> c_int;
}
// librte_eal
pub fn dpdk_rte_eal_init(argc: i32, argv: Vec<String>) -> i32 {
let mut args: Vec<*mut c_char> = argv.iter().map(|x| CString::new(x.clone()).unwrap().into_raw()).collect();
let retc: c_int = unsafe { rte_eal_init(argc as c_int, args.as_mut_ptr()) };
let ret: i32 = retc as i32;
ret
}
fn main() {
let args: Vec<String> = env::args().collect();
let ret: i32 = dpdk_rte_eal_init(args.len() as i32, args);
if ret < 0 {
exit(ret);
}
}
C main.c -
#include <stdio.h>
#include <string.h>
#include <rte_eal.h>
#include <rte_debug.h>
int
main(int argc, char **argv)
{
int ret;
ret = rte_eal_init(argc, argv);
if (ret < 0)
rte_panic("Cannot init EAL\n");
return 0;
}
我通过查看 DPDK 源代码并添加打印语句来查看不同之处进行了一些调查。 rte_eal_init() 函数位于 eal.c 中，并调用其他各种初始化函数。额外输出的触发器来自 eal_common_dev.c 中名为 rte_eal_dev_init() 的另一个函数。
rte_eal_dev_init() -
int
rte_eal_dev_init(void)
{
struct rte_devargs *devargs;
struct rte_driver *driver;
/*
* Note that the dev_driver_list is populated here
* from calls made to rte_eal_driver_register from constructor functions
* embedded into PMD modules via the PMD_REGISTER_DRIVER macro
*/
/* call the init function for each virtual device */
TAILQ_FOREACH(devargs, &devargs_list, next) {
if (devargs->type != RTE_DEVTYPE_VIRTUAL)
continue;
if (rte_eal_vdev_init(devargs->virt.drv_name,
devargs->args)) {
RTE_LOG(ERR, EAL, "failed to initialize %s device\n",
devargs->virt.drv_name);
return -1;
}
}
/* Once the vdevs are initalized, start calling all the pdev drivers */
TAILQ_FOREACH(driver, &dev_driver_list, next) {
if (driver->type != PMD_PDEV)
continue;
/* PDEV drivers don't get passed any parameters */
driver->init(NULL, NULL);
}
return 0;
}
我发现 Rust 程序进入了 rte_eal_dev_init() 函数，但从未进入 TAILQ_FOREACH() 宏的循环。如果我要像这样在宏的上方和下方添加打印语句 -
printf("Test before TAILQ_FOREACH\n");
TAILQ_FOREACH(driver, &dev_driver_list, next) {
printf("Test in TAILQ_FOREACH\n");
if (driver->type != PMD_PDEV)
continue;
/* PDEV drivers don't get passed any parameters */
driver->init(NULL, NULL);
}
这给了我以下 Rust 输出 -
~/Dev/rust_eal_init_test$ sudo target/debug/rust_eal_init_test
EAL: Detected 8 lcore(s)
EAL: No free hugepages reported in hugepages-2048kB
EAL: Probing VFIO support...
Test before TAILQ_FOREACH
~/Dev/rust_eal_init_test$
C 中的以下输出 -
~/Dev/c_eal_init_test$ sudo build/c_eal_init_test
EAL: Detected 8 lcore(s)
EAL: No free hugepages reported in hugepages-2048kB
EAL: Probing VFIO support...
Test before TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
PMD: bnxt_rte_pmd_init() called for (null)
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
Test in TAILQ_FOREACH
EAL: PCI device 0000:00:19.0 on NUMA socket -1
EAL: probe driver: 8086:153a rte_em_pmd
EAL: PCI device 0000:04:00.0 on NUMA socket -1
EAL: probe driver: 8086:1533 rte_igb_pmd
~/Dev/c_eal_init_test$
我发现TAILQ_FOREACH() 是在sys/queue.h 中定义的。据我了解，链接到静态库不应该导致库动态链接到其他东西的问题。这是正确的吗？
【问题讨论】：
-
听起来你可能没有将
TAIL_Q_FOREACH（可能是一个宏 thar 生成循环）转换为 Rust - 但你没有显示任何代码，所以无法判断。如果你让它运行，我不认为这是一个链接问题。 -
正如目前所写的，这个问题应该被关闭，因为：寻求调试帮助的问题（“为什么这段代码不起作用？”）必须包括所需的行为、特定的问题或错误以及在问题本身中重现它所需的最短代码。没有明确问题陈述的问题对其他读者没有用处。 edit 你的问题产生一个minimal reproducible example。
-
您的
printf完全改变了循环的行为。这就是为什么 if 语句上的大括号应该是强制性的。 -
感谢 Shepmaster 的输入，我今天会尝试编辑它以符合规则。
-
希望我所做的编辑符合最小、完整和可验证的规则