EE160 Programming for Engineers

What are compilation errors?

• errors that show up when the code is getting compiled, i.e. running gcc

Why do compilation errors occur?

• syntax
• missing punctations like ;
• misspelled function names like prinf
• wrong case like Prinf
• wrong function arguments like too many arguments or wrong types of arguments
• mismatched brackets like {{ }

How to use compilation errors?

• the error message will get you close to the line number of where the error occurred
• the error message will give you a sense of what's wrong
• compile often so you know exactly which part of the code you recently updated that is causing the error
• remove half the code so you can see which half is producing the error; repeat to narrow down the bad line of code

What are runtime errors?

• errors that show up when the code is executing, i.e. after compiling and running ./hello_world

Why do runtime errors occur?

• simple mistake
  • wrong data types, i.e. using int instead of float
  • wrong conversion specifier
  • not taking into account the edge cases, like if it's a negative number, a really small/big number, etc
  • pointers vs variables (addresses vs values)
  • wrong variable name
• logic
  • not accounting for a particular situation, i.e. edge case scenario like when a user enters a special character instead of a letter
  • variable gets altered in unexpected way
  • a simple mistake else where causes the error to other parts of the program
  • not allocating enough memory

How to fix runtime errors?

• trace through program and isolate possible areas of error
• use printf statements to figure out where the code is dying
• use printf statemetns to follow which logic branch is getting executed
• use printf statements to verify the variables you are expecting
• re-evaluate your algorithm

• Take a deep breath, go for a jog, take a shower, or do some yoga
• Sometimes the solution will just come to you after you take a break from it
• If you're still lost, then delete/comment out whatever you need to get the program working, even if it's just an empty main function
• Then add one line back at a time to see which line of code is causing the error (you don't have to be a genius to program, you have to be determined and persistent)
• Refer back to this lecture and see if there's any debugging methods you haven't tried
• Ask someone to look over your code with fresh eyes and see if they can catch anything you missed

fix fix_me.c:

The program is supposed to output The result is: -0.250000

Homework Problem 4.1, at the end of this problem you should submit to Laulima:

• a file named UHusername_04_1.c
• example:
  • zhaol_04_1.c

• fix fix_me.c by yourself

  • make sure the program can compile, run, and calculate the correct result
  • program is supposed to output: The result is: -0.250000

Homework Problem 4.2, at the end of this problem you should submit to Laulima:

• a file named UHusername_04_2.c
• example:
  • zhaol_04_2.c

• fix fix_me_too.c

  • make sure the program can compile, run, and print out the following:

    /\/\
    'The first number is $3'
    "The second number is 5.000000?"
    /|\The special character is "\"/|\