4.4.2 lint Message Formats

The lint program can, with certain options, show precise source file lines with pointers to the line position where the error occurred. The option enabling this feature is -errfmt=f, which causes lint to provide the following information:

• Source lines and positions

• Macro unfolding

• Error-prone stacks

For example, the following program, Test1.c, contains an error.

1 #include <string.h>
2 static void cpv(char *s, char* v, unsigned n)
3 { int i;
4   for (i=0; i<=n; i++){
5        *v++ = *s++;}
6 }
7 void main(int argc, char* argv[])
8 {
9     if (argc != 0){
10        cpv(argv[0], argc, strlen(argv[0]));}
11}

Using lint on Test1.c with the —errfmt=src option produces the following output::

% lint -errfmt=src -Nlevel=2 Test1.c
      |static void cpv(char *s, char* v, unsigned n)
      |            ^  line 2, Test1.c
      |
      |         cpv(argv[0], argc, strlen(argv[0]));
      |                      ^  line 10, Test1.c
warning: improper pointer/integer combination: arg #2
      |
      |static void cpv(char *s, char* v, unsigned n)
      |                               ^  line 2, Test1.c
      |
      |cpv(argv[0], argc, strlen(argv[0]));
      |                       ^ line 10, Test1.c
      |
      |        *v++ = *s++;
      |         ^  line 5, Test1.c
warning: use of a pointer produced in a questionable way
    v defined at Test1.c(2)    ::Test1.c(5)
      call stack:
          main()                ,    Test1.c(10)
          cpv()                 ,    Test1.c(5)

The first warning indicates two source lines that are contradictory. The second warning shows the call stack with the control flow leading to the error.

Another program, Test2.c, contains a different error:

1 #define AA(b) AR[b+l]
2 #define B(c,d) c+AA(d)
3
4 int x=0;
5
6 int AR[10]={1,2,3,4,5,6,77,88,99,0};
7
8 main()
9  {
10  int y=-5, z=5;
11  return B(y,z);
12 }

Using lint on Test2.c with the —errfmt= macro option produces the following output, showing the steps of macro substitution:

% lint -errfmt=macro Test2.c
      | return B(y,z);
      |        ^  line 11, Test2.c
      |
      |#define B(c,d) c+AA(d)
      |                 ^  line 2, Test2.c
      |
      |#define AA(b) AR[b+l]
      |                   ^  line 1, Test2.c
error: undefined symbol: l
|
      |    return B(y,z);
      |           ^  line 11, Test2.c
      |
      |#define B(c,d) c+AA(d)
      |                 ^  line 2, Test2.c
      |
      |#define AA(b) AR[b+l]
      |                   ^  line 1, Test2.c
variable may be used before set: l
lint: errors in Test2.c; no output created
lint: pass2 not run - errors in Test2.c