Like a variable in the C language, a function has an address — a location in memory. This fact shouldn’t be surprising to you. After all, the function has to sit somewhere. And my guess is that location doesn’t change as the program runs.
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\nA function’s address is an attribute used as an argument in several C language functions. You may have seen this requirement in some C Library functions and perhaps even used a function address in your own code.<\/p>\n
As an example, the qsort()<\/em> function’s fourth argument is the name of the function that compares the values:<\/p>\n Above, So how does that work?<\/p>\n Look at the qsort()<\/em> statement above. When a function is used as an argument, the parentheses are absent. With the parentheses, the function is called and it does whatever. Minus the parentheses, the function’s address is returned.<\/p>\n Here’s sample code:<\/p>\n In the first printf()<\/em> statement, the value generated by function()<\/em> is returned.<\/p>\n In the second printf()<\/em> statement, the address of function()<\/em> is returned.<\/p>\n Here’s how the output looks on my computer:<\/p>\n Obviously, the address shown on your screen will be different and output in a different format as well. The point is that without the parentheses, the compiler reads function as a memory location, a pointer.<\/p>\n As a pointer, a function also sports a variable type, which makes sense. If you want to get really weird, you can save a function’s address in a pointer variable and use that variable to call the function. I’ll show you that truly oddball construction in next week’s Lesson<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":" Grabbing the address of a function. Continue reading qsort(qarray,SIZE,sizeof(int),compare);<\/code><\/pre>\ncompare<\/code> is the name of the compare()<\/em> function, which compares two values. (See my Lesson<\/a> on the Quicksort.)<\/p>\n\r\n#include <stdio.h>\r\n\r\nint function(void)\r\n{\r\n return(42);\r\n}\r\n\r\nint main()\r\n{\r\n printf(\"The value of function() is %d\\n\",\r\n function());\r\n printf(\"The address of function() is %p\\n\",\r\n function);\r\n\r\n return(0);\r\n}<\/pre>\nThe value of function() is 42\r\nThe address of function() is 0x10e95ce90<\/code><\/pre>\n