ECE 103 Engineering ProgrammingChapter 9

gcc Compiler

Herbert G. Mayer, PSU CSStatus 6/19/2015

Initial content copied verbatim fromECE 103 material developed by

Professor Phillip Wong @ PSU ECE

Syllabus What’s This Blue Code? Compile C Source Code Execute Generated Object Code

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What’s This Blue Code?#include <stdio.h> // for printf()#define Max 4

short zag = -1;short prime[ Max ] = { 3, 5, 7, 11 }; // initializationvoid print_prime(){ // print_prime short i; for( i = 0; i < Max; i++ ) { printf( " prime[%1d] = %2d\n", i, prime[ i ] ); } //end for printf( " zag = %d\n\n", zag );} //end print_prime

int one(){ // one zag++; // side-effect return 1;} //end one

main( ){ // main print_prime(); prime[ zag + one() ] = prime[ zag + one() ]; // left or right first? print_prime();} //end main

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Compile Source Code

The GNU Project provides a freely available, open source C compiler called gcc

Syntax for compiling a program (command line):

gcc [options] file_list

where:gcc → compiler name (in lowercase)[options] → compilation options (optional)file_list → list of source and/or object files

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Typical GCC compilation options:

Option Description

-std=xxx

–std=c90 to compile to ISO C90 standard–std=c99 to compile to ISO C99 standard–std=gnu90 to compile to GNU C90 standard–std=gnu99 to compile to GNU C99 standard

-ansi Same effect as –std=c90

-pedantic Issue warning if C source is not strictly ISO compliant

-Wall Issue warnings on all questionable C constructs

-lmLink to the standard math library(required for some UNIX systems)

-o exec_file

Determines the name of the executable file(can be different from the source file name)

If -o is omitted, the default name is a.out (or a.exe).

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Example:Your source file is called prog1.c. Your compiler generates a default executable file named a.out

Type this at the command line (no extra checking):

gcc prog1.c

-or-

Type this at the command line (full checking):

gcc -ansi -pedantic -Wall prog1.c

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Example:Your source file is called mathprog.c. But you prefer the executable file to be named mprog.

Then type this command:

gcc -ansi -pedantic -Wall mathprog.c –o mprog

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Example:Your source files are ted.c and alice.c. You want the executable file to be named jupiter2.

Type this at the command line:

gcc -ansi -pedantic -Wall ted.c alice.c –o jupiter2

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Execute Generated Object Code

If the source file is compiled successfully, an executable (binary) file is created

The executable file can be run from the command line in Unix-like environments

Syntax for running the executable file:

efilename

where efilename is the name of the actual file you want to run.

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If the operating system complains that it cannot find the executable file in the current directory: Prefix the file's name with "./" Syntax: ./efilename

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Example1:Suppose your executable file is called a.out and it is stored in the current directory

To run it, type the following: ./a.out

On Unix, this also works: a.out

Example2:Suppose your executable file is called prog1 and it is stored in subdirectory HW2

To run it, type the following: HW2/prog1