我继承了一些非常旧的bison代码，处理这些代码已经有一段时间了，编译失败了，出现了一些警告和错误，这些警告我可以解决，但我不知道如何纠正这些错误。这里有一个例子：
给定这组定义：
%%
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)); }
%%
它们被编译为：
bison -d -y gram.y
gcc -std=c89 -c y.tab.c
我得到以下错误(这只是众多错误中的一个)：
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); }"
我将回答这个问题，因为它涉及的主题可能会给学习使用bison/yacc的学生和像OP这样编译旧代码并混淆错误来源的人带来困惑。
正如评论中所暗示的，这些错误与bison无关，而是来自于bison文件中包含的C代码，但不是bison的人工制品，也不是由bison或yacc多年来的变化引起的。它们是由C编译器多年来的变化引起的。现代的C编译器比以前的编译器宽容度低(更好)，尤其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来实现向后兼容性，当以前的编译器可能什么都没说或只发出警告时，它有时仍然会产生错误。
为了证明故障完全在C中，可以执行以下操作：
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
^
您可以看到，在C的几行中，gcc将输出与您所看到的相同的错误消息。
关于这个问题，以及如何解决这个问题，SO上有很多内容：
- C中的冲突类型错误
- 使用gcc编译c程序时发生冲突类型错误
- 得到"函数的冲突类型"；在C中，为什么
- C中的隐式函数声明
- 警告：函数的隐式声明
- 错误：函数的隐式声明'；create_proc_read_entry'；[-Weror=隐式函数声明]
脚注：可以关闭一些gcc错误，或通过使用#pragma或控制错误诊断级别将其减少为警告，但在这种情况下是不可能的。不支持gcc选项-Wno-error-implicit-function-declaration。线路：
#pragma GCC diagnostic warning "-Werror-implicit-function-declaration"
(或类似的)也不能消除错误。只是为了以防万一有人想知道
Bison中的类型冲突
在bison/yacc中使用类似代码时，许多人都会遇到bison检测到的代码类型不匹配的问题。也许值得在这方面添加一些注释，以使答案更加完整。通常情况下，在解析与语法类似的内容时，使用函数dlink、Link、newnode和attribute生成解析树。该树将由一些struct组成，并通过指向结构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，我们可以声明如下函数的原型：
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);
我们可以将其与您的语法相结合，以制作此文件：
%{
#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 ']'{ $$ = dlink($1, newnode($3, $5)); }
%%
也许你所拥有的就是这样的东西？如果我们把它通过bison和gcc，我们会得到很多警告，但它确实会生成代码。我注意到你说过你有很多警告。也许他们是这样的：
gram.y: In function 'yyparse':
gram.y:23:11: warning: assignment makes pointer from integer without a cast [enabled by default]
pgm: exp { pgm = $1; }
^
gram.y:25:5: warning: passing argument 2 of 'dlink' makes pointer from integer without a cast [enabled by default]
exp: list { $$ = 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)); }
^
这些对于野牛的新用户来说可能非常常见。为了消除这些警告，有必要通知bison如何使用类型，使其能够生成类型正确的代码。这是通过在bison代码中再添加几行来完成的。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单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到语法文件中，所有的错误和警告都会被消除，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一些方面，这些方面可能会影响新加入bison的用户或采用其他代码库的用户。