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guides:software:gcc:start [2020/07/19 14:28] – [Producing Additional Warnings] wikiadminguides:software:gcc:start [2022/08/02 11:59] (current) – external edit 127.0.0.1
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 ==== Some Useful Arguments ==== ==== Some Useful Arguments ====
  
-  * //--version// will display the version of g++ you are using.+  * //- -version// will display the version of g++ you are using.
     * <code>     * <code>
 $ g++ --version $ g++ --version
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 Compilers are also capable of analyzing source code to predict where this code may cause run time errors.    By turning on these warnings you are more likely to write code that conforms to the standard and less likely to have common runtime errors in  your code. Compilers are also capable of analyzing source code to predict where this code may cause run time errors.    By turning on these warnings you are more likely to write code that conforms to the standard and less likely to have common runtime errors in  your code.
  
-Your instructor may require one or more of the following flags when compiling code+Your instructor may require one or more of the following flags when compiling code:
  
   * //-Wpedantic//   * //-Wpedantic//
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     * Warn about uninitialized variables.     * Warn about uninitialized variables.
     * This flag requires //-O**n**// for some variables.     * This flag requires //-O**n**// for some variables.
 +      * See below.
   * //-Wshadow//   * //-Wshadow//
     * Warn when shadow variables are declared in a scope     * Warn when shadow variables are declared in a scope
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     * Warn when an implicit conversion may change a value.     * Warn when an implicit conversion may change a value.
  
 +Note:  There are **many** other warning producing flags.
  
 +For the following code:
 +<code c++>
 +#include <iostream>
 +
 +using namespace std;
 +
 +int main() {
 +    int a,b;
 +    int c;
 +
 +    if (a = b)
 +       cout << " a is 4" << endl;
 +       a = 5;
 +
 +    return 3.14;
 +}
 +</code>
 +
 +Compiling without additional flags produces no warnings.  But compiling with the listed flags produces
 +<code>
 +$ g++ bad.cpp
 +$ g++ -g -O3 -Wpedantic -Wall -Wextra -Wmisleading-indentation -Wunused -Wuninitialized -Wshadow -Wconversion bad.cpp
 +bad.cpp: In function 'int main()':
 +bad.cpp:10:11: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
 +   10 |     if (a = b)
 +      |         ~~^~~
 +bad.cpp:10:5: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
 +   10 |     if (a = b)
 +      |     ^~
 +bad.cpp:12:8: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
 +   12 |        a = 5;
 +      |        ^
 +bad.cpp:14:12: warning: conversion from 'double' to 'int' changes value from '3.1400000000000001e+0' to '3' [-Wfloat-conversion]
 +   14 |     return 3.14;
 +      |            ^~~~
 +bad.cpp:8:9: warning: unused variable 'c' [-Wunused-variable]
 +    8 |     int c;
 +      |         ^
 +bad.cpp:10:11: warning: 'b' is used uninitialized in this function [-Wuninitialized]
 +   10 |     if (a = b)
 +      |         ~~^~~
 +</code>
 +
 +You should use all command line flags specified by your instructor.  
 +
 +
 +Note: If you wish to avoid typing command line arguments, you may wish to investigate 
 +  * Makefiles
 +  * Command Line History
 ==== Other Arguments ==== ==== Other Arguments ====
  
guides/software/gcc/start.1595168934.txt.gz · Last modified: 2022/08/02 11:59 (external edit)