CodeBlocks常见编译错误（to be updated）
第一要则,不要直接点击”编译并且运行”,而是应该点击”编译(build)”按钮,这样可以保证警告不会被忽略,一些警告是非常有用的.
第二要则:有多个错误,要先处理最前面的错误,因为后面的错误可能前面的错误引发的.所以修改最前面的错误后就可以立即重新编译,往往可以看到所有的错误信息都不见了.
每一条信息是按字母排序，可以按序查找。
格式说明: 每一条错误都提供了样例程序,编译信息以及必要的说明
编译信息格式按 文件名，程序行数，编译错误信息组织，例如
E:\chen\dream\ex.c|6|error: break statement not within loop or switch|
使用说明: 使用关键字查找本文,如undeclared
a label can only be part of a statement and a declaration is not a statement|
break statement not within loop or switch
character constant too long for its type
'else' without a previous 'if'
expected declaration or statement at end of input
expected declaration specifiers or '...' before string constant
expected expression before 'X' token
expected primary-expression before '=' token
expected identifier or '(' before '}' token
expected '=', ',', ';', 'asm' or '__attribute__' before 'X' token
extra tokens at end of #include directive [enabled by default]|
format '%X' expects argument of type 'XXX',
implicit declaration of function 'XXX'
incompatible type for argument X of 'XXX
invalid preprocessing directive 'XXX
invalid suffix "X" on integer constant
lvalue required as left operand of assignment
missing terminating X character
情况一： missing terminating " character 漏掉了右侧的双引号
fatal error: XXX: No such file or directory
subscripted value is neither array nor pointer nor vector
suggest parentheses around '&&' within '||'（警告）
suggest parentheses around assignment used as truth value
too few arguments to function 'XXX'
a label can only be part of a statement and a declaration is not a statement|
标号不应该放在声明处
#include<stdio.h>
int main(void)
{
backward: //应该放在int语句下面
int i = 0, n, a[32];
scanf("%d", &n);
while(n > 0) {
a[i] = n % 2;
i = i + 1;
n = n / 2;
}
for(i--; i >= 0; i--)
printf("%d", a[i]);
printf("\n");
goto backward;
return 0;
}
E:\chen\dream\ex.c|5|error: a label can only be part of a statement and a declaration is not a statement|
break statement not within loop or switch
break必须在循环或switch里面。如果在if里面，if必须在循环或switch里面。
示例
#include <stdio.h>
int main(void)
{
int i=1;
if(i==1)
break;//在if里面是不可以的
return 0;
}
E:\chen\dream\ex.c|6|error: break statement not within loop or switch|
character constant too long for its type
#include <stdio.h>
int main()
{
char *s = 'hello,world\n'; //应该用双引号
return 0;
}
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|4|warning: character constant too long for its type [enabled by default]|
E:\chen\dream\ex.c|4|warning: initialization makes pointer from integer without a cast [enabled by default]|
解释:字符常量才用单引号
conflicting types for ‘XXX’
#include<stdio.h>
#include<math.h>
double pow(int x,int y) //math.h中已经有pow函数，两者不一致，可以取另外的名字
{
return x*y;
}
int main(void)
{
pow(3,5);
return 0;
}
E:\chen\dream\ex.c|3|error: conflicting types for 'pow'|
'else' without a previous 'if'
解释：else没有配对的if。
#include <stdio.h>
int main(void)
{
int year = 3;
scanf("%d", &year);
if(year % 7); //此处分号多余，导致后面的else没有配对
printf("yes\n");
else
printf("no\n");
return 0;
}
E:\chen\dream\ex.c|8|error: 'else' without a previous 'if'
empty character constant
#include <stdio.h>
int main(void)
{
char s[10]="123";
if(s[0] == '') //单引号中间有空格，而不是空的没有字符
printf("equal\n");
return 0;
}
E:\chen\dream\ex.c|5|error: empty character constant|
expected declaration or statement at end of input
#include <stdio.h>
int main()
{
int a = 3;
return 0; //后面漏掉}
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|error: expected declaration or statement at end of input|
解释: 程序没有写完整,漏掉了大括号。
expected declaration specifiers or '...' before string constant
int a,b;
scanf("%d %d",&a, &b); //连个main函数都没有
E:\chen\dream\ex.c|2|error: expected declaration specifiers or '...' before string constant|
expected expression before 'X' token
一般是因为写错了符号或者漏写了符号或者多敲了符号
示例一
#include <stdio.h>
int main(void)
{
int a;
scanf(%d", &a); //%前面少了双引号
return 0;
}
E:\chen\dream\ex.c|5|error: expected expression before '%' token|
示例二
#include <stdio.h>
int main(void)
{
int a = 3;
if(a= = 3) //==之间不能有空格
print("yes");
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|6|error: expected expression before '=' token|
E:\chen\dream\ex.c|7|warning: implicit declaration of function 'print' [-Wimplicit-function-declaration]|
E:\chen\dream\ex.c|5|warning: variable 'a' set but not used [-Wunused-but-set-variable]|
||=== Build failed: 1 error(s), 2 warning(s) (0 minute(s), 0 second(s)) ===|
示例三
if(s[i]=='a'||s[i]=='A')||s[i]=='e'||s[i]=='E'||s[i]=='i'||s[i]=='I'||s[i]=='o'||s[i]=='O'||s[i]=='u'||s[i]=='U')
error: expected expression before '||' token
注意'A'的后面多写了)
expected primary-expression before '=' token
if(l!==l1) //多写了=
error: expected primary-expression before '=' token
expected identifier or '(' before '}' token
示例一
#include <stdio.h>
int main()
{
return 0;
}
} //此处括号是多余的
E:\chen\dream\ex.c|7|error: expected identifier or '(' before '}' token|
示例二
#include <stdio.h>
int main();
{ //其实是这一行的前面多了分号
return 0;
}
E:\chen\dream\ex.c|3|error: expected identifier or '(' before '{' token|
expected '=', ',', ';', 'asm' or '__attribute__' before 'X' token
少了或者多写了符号
示例一
#include <stdio.h>
int main
{ //实际是main函数后面少了( )
return 0;
}
E:\chen\dream\ex.c|3|error: expected '=', ',', ';', 'asm' or '__attribute__' before '{' token|
示例二
include <stdio.h> //include前面少了#
int main()
{
return 0;
}
E:\chen\dream\ex.c|1|error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token|
示例三
#include <stdio.h>
int main(void)
{
int a
scanf("%d",&a); //前一行漏掉一个分号
return 0;
}
E:\chen\dream\ex.c|5|error: expected '=', ',', ';', 'asm' or '__attribute__' before 'scanf'|
示例四
int flag==0; //多写了一个=
error: expected '=', ',', ';', 'asm' or '__attribute__' before '==' token
expected ';' before ‘XXX’
少了分号
示例一
#include <stdio.h>
int main()
{
printf("hello,world\n")
return 0; //前一行漏掉一个分号
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|error: expected ';' before 'return'|
E:\chen\dream\ex.c|6|warning: control reaches end of non-void function [-Wreturn-type]|
||=== Build failed: 1 error(s), 1 warning(s) (0 minute(s), 0 second(s)) ===|
原因: 上一行的语句少了分号结束(本例中是printf这一行少了分号,但是编译器显示错误在return 0这一行).
示例二
#include <stdio.h>
int main(void)
{
int i;
for(i=1, i<10; i++) //for语句里面应该恰好有两个分号，i=1后面应该是分号
printf("%d",i);
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|warning: value computed is not used [-Wunused-value]|
E:\chen\dream\ex.c|5|error: expected ';' before ')' token|
||=== Build failed: 1 error(s), 1 warning(s) (0 minute(s), 0 second(s)) ===|
expected '(' before '{' token
for{b=1;b<=50;b++} //显然(被误写成了{
error: expected '(' before '{' token
expected ')' before 'X' token
一般是漏掉了)号，但是也有其他情况。
示例一
#include <stdio.h>
int main()
{
printf("hello,world\n"; //此处;前面漏掉了)
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|4|error: expected ')' before ';' token|
E:\chen\dream\ex.c|6|error: expected ';' before '}' token|
E:\chen\dream\ex.c|6|warning: control reaches end of non-void function [-Wreturn-type]|
||=== Build failed: 2 error(s), 1 warning(s) (0 minute(s), 2 second(s)) ===|
示例二
#include <stdio.h>
int main()
{
int a = 3;
printf("%d%d"a); //a前面有应该逗号把两个参数分开
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|error: expected ')' before 'a'|
E:\chen\dream\ex.c|5|warning: format '%d' expects a matching 'int' argument [-Wformat]|
E:\chen\dream\ex.c|4|warning: unused variable 'a' [-Wunused-variable]|
||=== Build failed: 1 error(s), 2 warning(s) (0 minute(s), 0 second(s)) ===|
示例三
printf("GCD=%d LCM=%d",gcd(m,n) lcm(m,n)); //lcm前面应该有逗号
Main.c:24:37: error: expected ')' before 'lcm'
示例四
while(scanf("%d %d",&sum,&n) !EOF){ //实际上是!=
extra tokens at end of #include directive [enabled by default]|
#include <stdio.h>#include <stdlib.h.> //每个预处理指令如#include应该单独占据一行
int main()
{
return 0;
}
E:\chen\dream\ex.c|1|warning: extra tokens at end of #include directive [enabled by default]|
format '%X' expects argument of type 'XXX',
示例一
#include <stdio.h>
int main()
{
int a;
scanf("%d", a); //应该是 &a
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|warning: format '%d' expects argument of type 'int *', but argument 2 has type 'int' [-Wformat]|
E:\chen\dream\ex.c|5|warning: 'a' is used uninitialized in this function [-Wuninitialized]|
||=== Build finished: 0 error(s), 2 warning(s) (0 minute(s), 3 second(s)) ===|
||=== Run: Debug in dream (compiler: GNU GCC Compiler) ===|
解释: 这个是警告,但是该警告往往是不能忽略,初学者一般是忘记了取址&符号
示例二：
#include <stdio.h>
int main(void)
{
int a=3, b=4;
printf("%d%d", a); //两个%d后面应该有两个参数，此处只有一个a，缺了b
return 0;
}
E:\chen\dream\ex.c|5|warning: format '%d' expects a matching 'int' argument [-Wformat]|
'gets' is deprecated
这个警告目前可以忽略，是说不鼓励使用gets
while(gets(str)!=NULL)
warning: 'gets' is deprecated (declared at /usr/include/stdio.h:638) [-Wdeprecated-declarations]
implicit declaration of function 'XXX'
解释: 缺少函数原型.
如果是调用库函数,可能没有包含头文件,示例没有加stdio.h.或者写错了函数名（例如把scanf写成Scanf）
如果是自定义的函数,记住调用之前一定要声明或者定义.
示例一
int main()
{
int a;
scanf("%d", &a);
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|4|warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]|
E:\chen\dream\ex.c|4|warning: incompatible implicit declaration of built-in function 'scanf' [enabled by default]|
||=== Build finished: 0 error(s), 2 warning(s) (0 minute(s), 0 second(s)) ===|
||=== Run: Debug in dream (compiler: GNU GCC Compiler) ===|
示例二
#include <stdio.h>
int main(void)
{
int a=3;
print("%d",&a); //函数名写错
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|warning: implicit declaration of function 'print' [-Wimplicit-function-declaration]|
obj\Debug\ex.o||In function `main':|
E:\chen\dream\ex.c|5|undefined reference to `print'|
||=== Build failed: 1 error(s), 1 warning(s) (0 minute(s), 0 second(s)) ===|
incompatible type for argument X of 'XXX
#include <math.h>
int main()
{
int a = sqrt("4"); //”4”错误
return 0;
}
E:\chen\dream\ex.c|4|error: incompatible type for argument 1 of 'sqrt'|
d:\program files (x86)\codeblocks\mingw\bin\..\lib\gcc\mingw32\4.7.1\..\..\..\..\include\math.h|157|note: expected 'double' but argument is of type 'char *'|
E:\chen\dream\ex.c|4|warning: unused variable 'a' [-Wunused-variable]|
||=== Build failed: 1 error(s), 1 warning(s) (0 minute(s), 0 second(s)) ===|
解释:调用函数时实参类型和形参类型不兼容.如示例实参是字符串(指针),而形参是double类型
invalid operands to binary X
#include <stdio.h>
int main(void)
{
int a;
scanf("%d"&a);//漏掉了逗号，把&当成二元运算符了
return 0;
}
E:\chen\dream\ex.c|5|error: invalid operands to binary & (have 'char *' and 'int')|
invalid preprocessing directive 'XXX
#inclede <iostream> //include写错了
int main()
{
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c|1|error: invalid preprocessing directive #inclede|
||=== Build failed: 1 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|
解释:预处理指令写错了.
invalid suffix "X" on integer constant
#include <stdio.h>
int main()
{
int a = 3, b;
b = 2a; //本意是2*a
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|error: invalid suffix "a" on integer constant|
E:\chen\dream\ex.c|4|warning: variable 'b' set but not used [-Wunused-but-set-variable]|
E:\chen\dream\ex.c|4|warning: unused variable 'a' [-Wunused-variable]|
||=== Build failed: 1 error(s), 2 warning(s) (0 minute(s), 0 second(s)) ===|
解释: 编译器把2a看成一个常数,a就是后缀,但是这个后缀不存在. 如3L, 2.5f的L和f就是合法的后缀.示例的错误是初学者有时候犯的,应该写成2*a.
lvalue required as left operand of assignment
解释：赋值号的左边应该是左值（一般而言是变量）
#include <stdio.h>
int main(void)
{
int a = 3;
if(a % 3 = 0) //此处实际是==号，误写为=
printf("YES");
return 0;
}
E:\chen\dream\ex.c|5|error: lvalue required as left operand of assignment|
missing terminating X character
情况一： missing terminating " character 漏掉了右侧的双引号
示例一
#include <stdio.h>
int main()
{
printf("hello,world\n);//漏掉了右边的双引号
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|4|warning: missing terminating " character [enabled by default]|
E:\chen\dream\ex.c|4|error: missing terminating " character|
E:\chen\dream\ex.c|5|error: expected expression before 'return'|
E:\chen\dream\ex.c|6|error: expected ';' before '}' token|
E:\chen\dream\ex.c|6|warning: control reaches end of non-void function [-Wreturn-type]|
||=== Build failed: 3 error(s), 2 warning(s) (0 minute(s), 0 second(s)) ===|
原因: 字符串少了应该用一对双引号,示例中右边的双引号漏掉了
示例二
#include <stdio.h>
int main(void)
{
print("yesn\");
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|4|warning: implicit declaration of function 'print' [-Wimplicit-function-declaration]|
E:\chen\dream\ex.c|4|warning: missing terminating " character [enabled by default]|
E:\chen\dream\ex.c|4|error: missing terminating " character|
E:\chen\dream\ex.c|5|error: expected expression before 'return'|
E:\chen\dream\ex.c|6|error: expected ';' before '}' token|
E:\chen\dream\ex.c|6|warning: control reaches end of non-void function [-Wreturn-type]|
||=== Build failed: 3 error(s), 3 warning(s) (0 minute(s), 0 second(s)) ===|
这个错误是把\n误写为 n\, 然后\起转义作用和双引号结合，导致编译器认为少了一个双引号
情况二、missing terminating ' character
char a='3; //很明显少了单引号
printf("%d %d %d\n"'a,b,c);//本例单引号实际上是逗号
情况三：missing terminating > character
#include<stdio.h //很明显少了>
error: missing terminating > character
fatal error: XXX: No such file or directory
写错文件名了，例如有写成stdio,h的。
示例一
#include <studio.h> //文件名写错了,stdio.h
int main()
{
int a, b;
scanf("%d%d", &a,&b);
return 0;
}
E:\chen\dream\ex.c|1|fatal error: studio.h: No such file or directory|
示例二 iostream不要用C提交，而是该用C++提交
#include<iostream>
redefinition of ‘XXX’
解释 XXX重复定义了
原因: (1) 忘了前面已经使用该名字定义标识符了,解决办法是使用新的名字即可.
(2)很多同学在已有的程序后面再写新的程序,导致两个main出现.解决办法删掉原来的或者创建一个新文件来写新程序.
#include <stdio.h>
int main()
{
return 0;
}
int main()
{
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\dream\ex.c|6|error: redefinition of 'main'|
E:\dream\ex.c|2|note: previous definition of 'main' was here|
||=== Build failed: 1 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|
subscripted value is neither array nor pointer nor vector
#include <stdio.h>
int main(void)
{
int a[3]={1,2,3}, n=4;
n[2]=1; //a误写成n，n不是数组类型，也不是指针，不可以[ ]运算
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|error: subscripted value is neither array nor pointer nor vector|
E:\chen\dream\ex.c|4|warning: variable 'n' set but not used [-Wunused-but-set-variable]|
E:\chen\dream\ex.c|4|warning: unused variable 'a' [-Wunused-variable]|
||=== Build failed: 1 error(s), 2 warning(s) (0 minute(s), 0 second(s)) ===|
suggest parentheses around '&&' within '||'（警告）
#include <stdio.h>
int isLeap(int year)
{
if(year % 400 == 0 || year % 4 == 0 && year % 100 != 0)
return 1;
else
return 0;
}
int main(void)
{
return 0;
}
E:\chen\dream\ex.c|4|warning: suggest parentheses around '&&' within '||' [-Wparentheses]|
解释：&&优先级比||高，为了明确此点，你可以加上括号消除这个警告。如下
if(year % 400 == 0 || (year % 4 == 0 && year % 100 != 0))
suggest parentheses around assignment used as truth value
#include <stdio.h>
int main()
{
int a = 3;
if(a = 4) // 此处是否为==而不是=
printf("equal\n");
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|warning: suggest parentheses around assignment used as truth value [-Wparentheses]|
解释: 虽然只是警告, 但是对于大部分初学者来说,往往是把等于”==”误写为赋值”=”
statement with no effect（警告）
语句没有作用
示例一
#include <stdio.h>
int main(void)
{
23; //显然这条语句没有任何作用，可以删除
}
E:\chen\dream\ex.c|4|warning: statement with no effect [-Wunused-value]|
示例二
#include <stdio.h>
int main(void)
{
int n;
n<=10000&&n>=1;//此表达式应该和if，while之类的结合使用，否则不起作用
return 0;
}
E:\chen\dream\ex.c|5|warning: statement with no effect [-Wunused-value]|
stray '\XXX' in program
总体来说是程序不认识的符号。
原因有
（1）由于中文输入法的缘故,使用了中文的标点符号(全角)，比如；，｝，＋,改成英文的标点半角符号就行了(搞不清全角半角的话直接切换到英文输入环境即可)。
（2）在某个平台下格式不同的文件拿到OJ提交
示例一
#include <stdio.h>
int main()
{
int a = 3；//这里分号是全角的
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|4|error: stray '\357' in program|
E:\chen\dream\ex.c|4|error: stray '\274' in program|
E:\chen\dream\ex.c|4|error: stray '\233' in program|
E:\chen\dream\ex.c|5|error: expected ',' or ';' before 'return'|
E:\chen\dream\ex.c|4|warning: unused variable 'a' [-Wunused-variable]|
E:\chen\dream\ex.c|6|warning: control reaches end of non-void function [-Wreturn-type]|
||=== Build failed: 4 error(s), 2 warning(s) (0 minute(s), 5 second(s)) ===|
示例二： int main（void） //注意这里的括号
示例三
v#include <stdio.h> //前面多了一个v，导致#无法识别为预处理指令，#必须在最前面
int main(void)
{
int a#b; //#要么是逗号分成两个标志符,要么是字母构成一个完整的标识符
printf("no"\n); //\n应该放到双引号里面
return 0;
}
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\ex.c|1|error: stray '#' in program|
E:\chen\dream\ex.c|1|error: unknown type name 'v'|
E:\chen\dream\ex.c|1|error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token|
E:\chen\dream\ex.c|4|error: stray '#' in program|
E:\chen\dream\ex.c|5|error: stray '\' in program|
||=== Build failed: 5 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|
示例四：
rem=x%2;x=x\2; // 除号写错了
error: stray '\' in program
too few arguments to function 'XXX'
#include <stdio.h>
int main()
{
int a;
scanf(); //scanf里面没有参数
return 0;
}
E:\chen\dream\ex.c||In function 'main':|
E:\chen\dream\ex.c|5|error: too few arguments to function 'scanf'|
解释:调用函数是参数个数少了
‘XXX’ undeclared
解释 你使用了标识符‘XXX’,但是没有看到它的定义
原因 (1)你真正忘记定义变量就直接使用了,本例就是这种情况。
(2)写错了变量(标识符)的名字,导致前后不一致,还有注意C语言区分大小写 .解决办法是保证前后使用同一个标识符
(3)写错了关键字,C语言的很多关键字都是英文单词,如continue,return，else等等,写错了改正过来即可
(4)把数字0误写成字母o
(5)使用了头文件常量，但是没有#include头文件。例如使用EOF，NULL要#include <stdio.h>
示例一
#include <stdio.h>
int main()
{
a = 3;
return 0;
}
E:\dream\ex.c 4 error: 'a' undeclared (first use in this function)|
E:\dream\ex.c 4 note: each undeclared identifier is reported only once for each function it appears in
示例二
#include <stdio.h>
int main(void)
{
int a = 3;
if(a % 3 == o) //有趣之处数字0误写成字母o
print("yes");
return 0;
}
E:\chen\dream\ex.c|5|error: 'o' undeclared (first use in this function)|
undefined reference to ‘XXX’
解释:
你调用了’xxx’(例子中是print)函数，但是在目标文件中却找不到它
原因
1 拼错了函数的名字,尤其要注意大小写.例子是printf，漏掉了f
2 真正漏掉了这个函数项目中要添加对应的函数(或文件)
3. 如果出现undefined reference to `WinMain@16' (或main）一般是main的函数名写错了,例如误写成mian. 还有可能就是程序中没有main函数.
4. 调用了非标准库函数，如getch()
示例
#include <stdio.h>
int main()
{
print("hello,world\n");
return 0;
}
编译信息
In function `main':
E:\dream\ex.c 4 undefined reference to `print'
unknown type name 'fioat'
写错了类型名
fioat p(float n); //很明显应该是float
error: unknown type name 'fioat'
unused variable 'XXX'
#include <stdio.h>
int main()
{
int a = 3; //a在后面没有被用到
return 0;
}
E:\chen\dream\ex.c|4|warning: unused variable 'a' [-Wunused-variable]|
解释:这是一个警告,如果一个变量未使用,意味着删掉它对程序没有影响.不删掉也可以,只是多余而已.
||=== Build: Debug in dream (compiler: GNU GCC Compiler) ===|
E:\chen\dream\main.cpp||In function 'SElemType GetTop(SqStack)':|
E:\chen\dream\main.cpp|38|warning: control reaches end of non-void function [-Wreturn-type]|
