编译时,我遇到了很多次:
gcc -o index.o -c -D_FILE_OFFSET_BITS=64 "-D FUSE_USE_VERSION=31" index.c
index.c:40:12: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types]
.write = o_write,
^~~~~~~
保险丝的文档往往不一致且稀疏,因此我在GitHub上查找其他文件系统实现,以找到适当的方法签名。
在这种情况下,我的问题是:
int o_write(const char*, char*, size_t, off_t, struct fuse_file_info*);
应该是
int o_write(const char*, const char*, size_t, off_t, struct fuse_file_info*);
我的问题是:
当我看到此警告时,是否有一种简单的方法可以知道哪种指针类型是假定的?我花了很多时间在SSHF中追踪适当的实现,但是我觉得有一种更简单的方法。
这或多或少是mcve(最小,完整,可验证的示例),可重现您显示的错误消息:
#include <sys/types.h> // size_t, off_t
struct fuse_file_info;
struct whatever
{
int (*write)(const char*, const char*, size_t, off_t, struct fuse_file_info*);
};
extern int o_wrong(const char*, char*, size_t, off_t, struct fuse_file_info*);
extern int o_write(const char*, const char*, size_t, off_t, struct fuse_file_info*);
struct whatever v1 = { .write = o_wrong };
struct whatever v2 = { .write = o_write };
当包含所显示的代码的文件fuse37.c
使用GCC 7.2.0(在Mac运行MacOS High Sierra 10.13.2)上,我得到:
$ gcc -O3 -g -std=c11 -Wall -Wextra -Werror -c fuse37.c
fuse37.c:13:33: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
struct whatever v1 = { .write = o_wrong };
^~~~~~~
fuse37.c:13:33: note: (near initialization for ‘v1.write’)
cc1: all warnings being treated as errors
$
" note"行中的辅助信息告诉您,您需要查找write
成员的定义(结构类型struct whatever
)。
当您将错误的类型参数传递给函数调用时,您会收到更好的消息:
$ cat fuse47.c
struct gizmotron;
struct megatron;
extern void calumniator(struct gizmotron *ptr);
extern void transformer(struct megatron *arg);
void calumniator(struct gizmotron *ptr)
{
transformer(ptr);
}
$ gcc -O3 -g -std=c11 -Wall -Wextra -Werror -Wmissing-prototypes -Wstrict-prototypes -c fuse47.c
fuse47.c: In function ‘calumniator’:
fuse47.c:9:17: error: passing argument 1 of ‘transformer’ from incompatible pointer type [-Werror=incompatible-pointer-types]
transformer(ptr);
^~~
fuse47.c:5:13: note: expected ‘struct megatron *’ but argument is of type ‘struct gizmotron *’
extern void transformer(struct megatron *arg);
^~~~~~~~~~~
cc1: all warnings being treated as errors
$
现在,您可以看到该注释明确有关预期类型和接收的类型。我不确定初始化中缺少额外信息(而不是功能呼叫)是故意的还是监督的。由于一个诊断是可能的,另一个也应该是。可能值得询问海湾合作委员会维护团队是否可以升级。