我继承了一些非常古老的野牛代码，自从我处理了这个问题以来已经有一段时间了，编译因一些警告和错误而失败，我可以解决警告，但我不知道如何纠正错误。这是一个例子：
鉴于这套定义：
%%
pgm: exp { pgm = $1; }
exp: list { $$ = dlink(newnode(NULL,NULL),$1); }
| exp ';' list { $$ = Link($1, dlink(newnode(NULL,NULL),$3)); }
list: rec
| list ',' rec { $$ = Link($1, $3); }
rec: /* null */ { $$ = newnode(NULL, NULL); }
| path
| path '@' NAME { $$ = attribute($1, $3); }
| path '(' list ')' { $$ = dlink($1, $3); }
path: NAME { $$ = newnode($1, NULL); }
| path '.' NAME { $$ = dlink($1, newnode($3, NULL)); }
| path '[' INT ']' { $$ = dlink($1, newnode($3, $3)); }
| path '[' INT '-' INT ']'{ $$ = dlink($1, newnode($3, $5)); }
%%
编译为：
bison -d -y gram.y
gcc -std=c89 -c y.tab.c
我收到以下错误（这只是其中之一）：
gram.y: At top level:
gram.y:218:1: error: conflicting types for newnode
newnode(name, range)
^
gram.y:49:26: note: previous implicit declaration of newnode was here
"exp: list { $$ = dlink(newnode(NULL,NULL),$1); }"
答案 0 :(得分：2)
我会回答这个问题，因为它涉及的主题可能会导致学习使用bison / yacc的学生和那些正在编译旧代码并且错误来自哪里的混淆
正如评论中暗示的那样，错误与野牛完全无关，而是来自野牛文件中包含的C代码，但不是野牛的人工制品，也不是由野牛或yacc的变化引起的这些年。它们是由多年来C编译器的变化引起的。现代C编译器比以前的旧编译器更不容忍（更好），特别是在函数调用和参数检查方面。即使在现代编译器上选择选项以实现向后兼容性时，当前一个编译器可能没有说什么或只给出警告时，它有时仍然会产生错误。
为了证明故障完全在C中，人们可以做到以下几点：
Prompt> gcc -c -xc -std=c89 -
main () {
#line 49 "gram.y"
int a = newnode(a,1);
int * b = newnode(1,1);
}
void *
#line 218 "gram.y"
newnode(name, range)
int name,
range;
{
}
^Z
gram.y: In function 'main':
gram.y:50:12: warning: initialization makes pointer from integer without a cast
[enabled by default]
^
gram.y: At top level:
gram.y:218:1: error: conflicting types for 'newnode'
gram.y:49:10: note: previous implicit declaration of 'newnode' was here
^
你可以看到，在几行C中，gcc将输出你看到的相同错误信息。
关于这个问题有很多关于它的问题，以及如何解决这个问题：
脚注：可以关闭一些gcc错误，或者使用#pragma将其减少为警告，或者控制错误诊断的级别，但在这种情况下无法实现。 gcc option -Wno-error-implicit-function-declaration is not supported。{{3}}。这一行：
#pragma GCC diagnostic warning "-Werror-implicit-function-declaration"
（或类似）也不能消除错误。只要提到它，万一有人想知道
许多人在使用bison / yacc中的类似代码做时，他们的代码中的类型不匹配会被bison检测到。可能值得添加一些注释，以使答案更完整。通常情况下，在解析类似于语法的内容时，会使用函数dlink，Link，newnode和attribute创建解析树。该树将由一些struct构成，并通过指向struct struct *的指针链接，如下所示：
struct treeNode {
int item1,item2;
struct treeNode *left;
struct treeNode *right;
};
typedef struct treeNode TREE_NODE;
typedef TREE_NODE *BINARY_TREE;
为了避免前面显示的隐式函数类型的问题，我们可以为这样的函数声明原型：
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
BINARY_TREE newnode(int item1, int item2);
BINARY_TREE attribute(BINARY_TREE left, int item);
BINARY_TREE Link(BINARY_TREE left, BINARY_TREE right);
我们可以将它与你的语法结合起来制作这个文件：
%{
#define NULL 0
struct treeNode {
int item1,item2;
struct treeNode *left;
struct treeNode *right;
};
typedef struct treeNode TREE_NODE;
typedef TREE_NODE *BINARY_TREE;
BINARY_TREE pgm;
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
BINARY_TREE newnode(int item1, int item2);
BINARY_TREE attribute(BINARY_TREE left, int item);
BINARY_TREE Link(BINARY_TREE left, BINARY_TREE right);
%}
%token INT NAME
%%
pgm: exp { pgm = $1; }
exp: list { $$ = dlink(newnode(NULL,NULL),$1); }
| exp ';' list { $$ = Link($1, dlink(newnode(NULL,NULL),$3)); }
list: rec
| list ',' rec { $$ = Link($1, $3); }
rec: /* null */ { $$ = newnode(NULL, NULL); }
| path
| path '@' NAME { $$ = attribute($1, $3); }
| path '(' list ')' { $$ = dlink($1, $3); }
path: NAME { $$ = newnode($1, NULL); }
| path '.' NAME { $$ = dlink($1, newnode($3, NULL)); }
| path '[' INT ']' { $$ = dlink($1, newnode($3, $3)); }
| path '[' INT '-' INT ']'{ $$ = dlink($1, newnode($3, $5)); }
%%
你可能拥有的是什么？如果我们把它通过bison和gcc我们得到很多警告，但它确实产生了代码。我注意到你说你有很多警告。也许他们就像这样：
gram.y: In function 'yyparse':
gram.y:23:11: warning: assignment makes pointer from integer without a cast [enabled by default]
pgm: exp { pgm = $1; }
^
gram.y:25:5: warning: passing argument 2 of 'dlink' makes pointer from integer without a cast [enabled by default]
exp: list { $$ = dlink(newnode(NULL,NULL),$1); }
^
gram.y:14:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
^
gram.y:25:18: warning: assignment makes integer from pointer without a cast [enabled by default]
exp: list { $$ = dlink(newnode(NULL,NULL),$1); }
^
gram.y:26:5: warning: passing argument 2 of 'dlink' makes pointer from integer without a cast [enabled by default]
| exp ';' list { $$ = Link($1, dlink(newnode(NULL,NULL),$3)); }
^
gram.y:14:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
gram.y:25:18: warning: assignment makes integer from pointer without a cast [enabled by default]
exp: list { $$ = dlink(newnode(NULL,NULL),$1); }
^
gram.y:26:5: warning: passing argument 2 of 'dlink' makes pointer from integer without a cast [enabled by default]
| exp ';' list { $$ = Link($1, dlink(newnode(NULL,NULL),$3
)); }
^
gram.y:14:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
^
gram.y:26:5: warning: passing argument 1 of 'Link' makes pointer from integer without a cast [enabled by default]
| exp ';' list { $$ = Link($1, dlink(newnode(NULL,NULL),$3
)); }
^
gram.y:17:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE Link(BINARY_TREE left, BINARY_TREE right);
^
gram.y:26:15: warning: assignment makes integer from pointer without a cast [enabled by default]
| exp ';' list { $$ = Link($1, dlink(newnode(NULL,NULL),$3
)); }
^
gram.y:29:5: warning: passing argument 1 of 'Link' makes pointer from integer without a cast [enabled by default]
| list ',' rec { $$ = Link($1, $3); }
^
gram.y:17:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE Link(BINARY_TREE left, BINARY_TREE right);
^
gram.y:29:5: warning: passing argument 2 of 'Link' makes pointer from integer without a cast [enabled by default]
| list ',' rec { $$ = Link($1, $3); }
^
gram.y:17:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE Link(BINARY_TREE left, BINARY_TREE right);
^
gram.y:29:15: warning: assignment makes integer from pointer without a cast [enabled by default]
| list ',' rec { $$ = Link($1, $3); }
^
gram.y:31:15: warning: assignment makes integer from pointer without a cast [enabled by default]
rec: /* null */ { $$ = newnode(NULL, NULL); }
^
gram.y:33:5: warning: passing argument 1 of 'attribute' makes pointer from integer without a cast [enabled by default]
| path '@' NAME { $$ = attribute($1, $3); }
^
gram.y:16:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE attribute(BINARY_TREE left, int item);
^
gram.y:33:15: warning: assignment makes integer from pointer without a cast [enabled by default]
| path '@' NAME { $$ = attribute($1, $3); }
^
gram.y:34:5: warning: passing argument 1 of 'dlink' makes pointer from integer without a cast [enabled by default]
| path '(' list ')' { $$ = dlink($1, $3); }
^
gram.y:14:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
^
gram.y:34:5: warning: passing argument 2 of 'dlink' makes pointer from integer without a cast [enabled by default]
| path '(' list ')' { $$ = dlink($1, $3); }
^
gram.y:14:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
^
gram.y:34:15: warning: assignment makes integer from pointer without a cast [enabled by default]
| path '(' list ')' { $$ = dlink($1, $3); }
^
gram.y:36:15: warning: assignment makes integer from pointer without a cast [enabled by default]
path: NAME { $$ = newnode($1, NULL); }
^
gram.y:37:5: warning: passing argument 1 of 'dlink' makes pointer from integer without a cast [enabled by default]
| path '.' NAME { $$ = dlink($1, newnode($3, NULL)); }
^
gram.y:14:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
^
gram.y:37:15: warning: assignment makes integer from pointer without a cast [enabled by default]
| path '.' NAME { $$ = dlink($1, newnode($3, NULL)); }
^
gram.y:38:5: warning: passing argument 1 of 'dlink' makes pointer from integer without a cast [enabled by default]
| path '[' INT ']' { $$ = dlink($1, newnode($3, $3)); }
^
gram.y:14:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
^
gram.y:38:15: warning: assignment makes integer from pointer without a cast [enabled by default]
| path '[' INT ']' { $$ = dlink($1, newnode($3, $3)); }
^
gram.y:39:5: warning: passing argument 1 of 'dlink' makes pointer from integer without a cast [enabled by default]
| path '[' INT '-' INT ']'{ $$ = dlink($1, newnode($3, $5)); }
^
gram.y:14:13: note: expected 'BINARY_TREE' but argument is of type 'YYSTYPE'
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
^
gram.y:39:15: warning: assignment makes integer from pointer without a cast [enabled by default]
| path '[' INT '-' INT ']'{ $$ = dlink($1, newnode($3, $5)); }
^
这对于新的野牛用户来说非常普遍。要消除这些警告，必须告知bison如何使用类型来使其生成类型正确的代码。这是通过在野牛代码中增加几行来完成的。首先，我们必须告诉它语法规则操作可以返回的类型：
%union {
BINARY_TREE tVal;
int iVal;
}
然后我们必须告诉它为各个令牌和规则操作返回的类型：
%token <iVal> NAME INT
%type <tVal> exp list rec path
如果我们将这些插入语法文件中，所有错误和警告都将被删除，我们得到：
%{
#define NULL 0
struct treeNode {
int item1,item2;
struct treeNode *left;
struct treeNode *right;
};
typedef struct treeNode TREE_NODE;
typedef TREE_NODE *BINARY_TREE;
BINARY_TREE pgm;
BINARY_TREE dlink(BINARY_TREE left, BINARY_TREE right);
BINARY_TREE newnode(int item1, int item2);
BINARY_TREE attribute(BINARY_TREE left, int item);
BINARY_TREE Link(BINARY_TREE left, BINARY_TREE right);
%}
%union {
BINARY_TREE tVal;
int iVal;
}
%token <iVal> NAME INT
%type <tVal> exp list rec path
%%
pgm: exp { pgm = $1; }
exp: list { $$ = dlink(newnode(NULL,NULL),$1); }
| exp ';' list { $$ = Link($1, dlink(newnode(NULL,NULL),$3)); }
list: rec
| list ',' rec { $$ = Link($1, $3); }
rec: /* null */ { $$ = newnode(NULL, NULL); }
| path
| path '@' NAME { $$ = attribute($1, $3); }
| path '(' list ')' { $$ = dlink($1, $3); }
path: NAME { $$ = newnode($1, NULL); }
| path '.' NAME { $$ = dlink($1, newnode($3, NULL)); }
| path '[' INT ']' { $$ = dlink($1, newnode($3, $3)); }
| path '[' INT '-' INT ']'{ $$ = dlink($1, newnode($3, $5)); }
%%
我希望我在C代码中发现了类型冲突的某些方面，这些方面可能会影响新手野牛或采用别人代码库的用户。