Example

$ cat bitfield.c

struct { int bit:1; } s;

void test()

{

s.bit = 1;

}

$ cc -c +wlint bitfield.c

"bitfield.c", line 1: warning #2108-D: signed bit field of length 1

struct { int bit:1; } s;

"bitfield.c", line 5: warning #4251-D: the assignment has an excessive size for a bit field

s.bit = 1;

Other notable examples of warnings enabled with the +wlint option:

•Argument is incompatible with formal parameter

•Function declared implicitly

•Function is re-declared after being called

•Type conversion may truncate value

•Unsigned value cannot be less than zero

•Missing return statement at end of non-void function

•Nested comment is not allowed

•Signed bitfield of length 1

•Memory leak

•Potential null pointer dereference

•Detection of uncaught exceptions

•Uninitialized variables

+w64bit

This option enables warnings that help you detect potential problems in converting 32-bit applications to 64-bit. The +w64bit option applies both to 32 bit and 64 bit compilers. It is equivalent to the +M2 option.

Some of the checks performed are:

•64bit value is implicitly converted to a 32bit value, e.g. long to int.

•Pointer to 4-byte aligned object implicitly converted to a pointer to 8-byte aligned object.

Example

$ cat convert.c

int *int_to_ptr (int i)

{

return (int *)i;

}

$ cc –c +w64bit convert.c

"convert.c", line 3: warning #4231-D: 64 bit migration: conversion between types of different sizes has occurred (from "int" to "int * ”)

return (int *)i;