结构和数组的定义 [英] Definition of structures and arrays
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问题描述
我有以下的code：
struct dmparam {
char *p;
char *v;
};
struct dmobj {
int a;
int b;
struct dmparam *dmparam;
};
struct dmarray {
struct dmobj *dmobj;
struct dmentry {
int func;
struct dmarray *dmarray;
} *dmentry;
};
struct dmarray atest = {
{//objs
{1, 11, NULL},
{2, 22,
{//params
{"p1", "v1"},
{"p2", "v2"},
}//params
}
},//objs
{//arays
{101, {
{//objs
{1, 11, NULL},
{2, 22,
{//params
{"p1", "v1"},
{"p2", "v2"},
}//params
}
},//objs
NULL
}
}
}//arrays
};
这code生成以下编译警告：
This code generate the following compilation warnings:
test.c:26:2: warning: braces around scalar initializer [enabled by default]
{//objs
^
test.c:26:2: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:27:2: warning: braces around scalar initializer [enabled by default]
{1, 11, NULL},
^
test.c:27:2: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:27:2: warning: initialization makes pointer from integer without a cast [enabled by default]
test.c:27:2: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:27:2: warning: excess elements in scalar initializer [enabled by default]
test.c:27:2: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:27:2: warning: excess elements in scalar initializer [enabled by default]
test.c:27:2: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:28:2: warning: braces around scalar initializer [enabled by default]
{2, 22,
^
test.c:28:2: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:28:2: warning: initialization makes pointer from integer without a cast [enabled by default]
test.c:28:2: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:28:2: warning: excess elements in scalar initializer [enabled by default]
test.c:28:2: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:29:3: warning: braces around scalar initializer [enabled by default]
{//params
^
test.c:29:3: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:30:3: warning: braces around scalar initializer [enabled by default]
{"p1", "v1"},
^
test.c:30:3: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:30:3: warning: initialization from incompatible pointer type [enabled by default]
test.c:30:3: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:30:3: warning: excess elements in scalar initializer [enabled by default]
test.c:30:3: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:31:3: warning: braces around scalar initializer [enabled by default]
{"p2", "v2"},
^
test.c:31:3: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:31:3: warning: initialization from incompatible pointer type [enabled by default]
test.c:31:3: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:31:3: warning: excess elements in scalar initializer [enabled by default]
test.c:31:3: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:31:3: warning: excess elements in scalar initializer [enabled by default]
test.c:31:3: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:32:3: warning: excess elements in scalar initializer [enabled by default]
}//params
^
test.c:32:3: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:33:2: warning: excess elements in scalar initializer [enabled by default]
}
^
test.c:33:2: warning: (near initialization for ‘atest.dmobj’) [enabled by default]
test.c:35:2: warning: braces around scalar initializer [enabled by default]
{//arays
^
test.c:35:2: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:36:3: warning: braces around scalar initializer [enabled by default]
{101, {
^
test.c:36:3: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:36:3: warning: initialization makes pointer from integer without a cast [enabled by default]
test.c:36:3: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:36:3: warning: braces around scalar initializer [enabled by default]
test.c:36:3: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:37:5: warning: braces around scalar initializer [enabled by default]
{//objs
^
test.c:37:5: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:38:5: warning: braces around scalar initializer [enabled by default]
{1, 11, NULL},
^
test.c:38:5: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:38:5: warning: initialization makes pointer from integer without a cast [enabled by default]
test.c:38:5: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:38:5: warning: excess elements in scalar initializer [enabled by default]
test.c:38:5: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:38:5: warning: excess elements in scalar initializer [enabled by default]
test.c:38:5: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:39:5: warning: braces around scalar initializer [enabled by default]
{2, 22,
^
test.c:39:5: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:39:5: warning: initialization makes pointer from integer without a cast [enabled by default]
test.c:39:5: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:39:5: warning: excess elements in scalar initializer [enabled by default]
test.c:39:5: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:40:6: warning: braces around scalar initializer [enabled by default]
{//params
^
test.c:40:6: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:41:6: warning: braces around scalar initializer [enabled by default]
{"p1", "v1"},
^
test.c:41:6: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:41:6: warning: initialization from incompatible pointer type [enabled by default]
test.c:41:6: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:41:6: warning: excess elements in scalar initializer [enabled by default]
test.c:41:6: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:42:6: warning: braces around scalar initializer [enabled by default]
{"p2", "v2"},
^
test.c:42:6: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:42:6: warning: initialization from incompatible pointer type [enabled by default]
test.c:42:6: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:42:6: warning: excess elements in scalar initializer [enabled by default]
test.c:42:6: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:42:6: warning: excess elements in scalar initializer [enabled by default]
test.c:42:6: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:43:6: warning: excess elements in scalar initializer [enabled by default]
}//params
^
test.c:43:6: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:44:5: warning: excess elements in scalar initializer [enabled by default]
}
^
test.c:44:5: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:47:3: warning: excess elements in scalar initializer [enabled by default]
}
^
test.c:47:3: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
test.c:47:3: warning: excess elements in scalar initializer [enabled by default]
test.c:47:3: warning: (near initialization for ‘atest.dmentry’) [enabled by default]
什么我米做错了吗？
What I m doing wrong?
什么是写这个的最佳方式？
What's the best way to write this?
推荐答案
这code编译作为一个完整的源文件：
This code compiles as a complete source file:
struct dmparam {
char *p;
char *v;
};
struct dmobj {
int a;
int b;
struct dmparam *dmparam;
};
struct dmarray {
struct dmobj *dmobj;
struct dmentry {
int func;
struct dmarray *dmarray;
} *dmentry;
};
struct dmparam dp1 = { "abc", "xyz" };
struct dmparam dp2 = { "Mercury", "Uranus" };
struct dmobj do1 = { 1, 1, &dp1 };
struct dmobj do2 = { 2, -987, &dp2 };
struct dmentry de1 = { 0, 0 };
struct dmarray da1 = { &do1, &de1 };
注意，你有有效的：
Observe that you effectively have:
struct dmentry {
int func;
struct dmarray *dmarray;
};
struct dmarray {
struct dmobj *dmobj;
struct dmentry *dmentry;
};
所以在每个只有两个项目结构dmarray ，两个指针。此外，结构dmentry 的范围不局限于;在C ++的规则是不同的。
So there are only two items in each struct dmarray, both pointers. Also, the struct dmentry is not restricted in scope; the rules in C++ are different.
所有这些是标准的C90 code（以及C99和C11）。在C99或更高版本，你也可以做初始化是这样的：
All that is standard C90 code (as well as C99 and C11). In C99 or later, you can also do the initialization like this:
struct dmarray da2 =
{
.dmobj = &(struct dmobj){ 9, 99, &(struct dmparam){ "Frigid", "Roasting" } },
.dmentry = &(struct dmentry){ 1, &(struct dmarray){ 0, 0 } }
};
请注意，你最终需要用一个指针结构dmarray 当你初始化一个又一个。我躲开并在嵌套结构使用空指针，但如果你想，你可以走得更深。
Note that you end up with needing a pointer to a struct dmarray while you're initializing another one. I ducked and use a null pointer in the nested structure, but you could go deeper if you wanted to.
为了记录时，code的Mac OS X上使用10.10.5海湾合作委员会测试（实际上铛）根据X code 6.4
Just for the record, the code was tested on Mac OS X 10.10.5 using 'gcc' (actually clang) from XCode 6.4:
$ gcc -std=c99 -pedantic -O3 -g -Wall -Wextra -Werror -c so.32014285.c
$ gcc --version
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn)
Target: x86_64-apple-darwin14.5.0
Thread model: posix
$
有是一个外的机会，尽管请求迂腐坚持C99标准，GCC是让通过扩展。
There's an outside chance that despite requesting pedantic adherence to the C99 standard, GCC is letting an extension through.
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