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#ActualServant of the Lord

Posted 26 January 2013 - 09:31 AM

Apparently GCC catches it also. Here's my expected results before compiling and before reading others' comments:

1. Without using a compiler look at the code. Would you expect any warnings or errors from the compiler? Why?

"test_func() = one;"- Some kind of 'Assigning to r-value/temporary' warning, since test_func() isn't returning by reference.
 
Also, test_func(void) should be test_func(), no need for the 'void' there. I don't know if a warning will result. Probably something like "explicit void argument - compile with -ANSI to disable warning"
 

2. What would you expect the output to be if it compiled?

Undefined gibberish value - whatever 'static number v' initially resolves to, because it has never been assigned anything.
 

3. Now compare your results to what actually happens when you compile it. Is it what you expected?

Using GCC/MinGW 4.7.2:
 
I didn't get the warning I expected on assigning "test_func() = one;",
instead I got an *error* on on the member variable assignment version: "test_func().x += 1.0f;"
 
error: using temporary as lvalue [-fpermissive]
 
 
 
I only found out yesterday that this is valid and standardized C++:
const int &refToTemp = 357;
...it just only lasts to the end of the scope that the expression is contained in. Still it's useful for avoiding a copy in some circumstances, which is why I looked it up:
//Only makes a copy if 'condition' is false.
const std::string &myString = ( ...condition... ? this->memberString : this->GetCopyOfSubStr_ReturnByValue());
this->UseString(myString);

#4Servant of the Lord

Posted 26 January 2013 - 09:31 AM

Apparently GCC catches it also. Here's my expected results before compiling and before reading others' comments:

1. Without using a compiler look at the code. Would you expect any warnings or errors from the compiler? Why?

"test_func() = one;"- Some kind of 'Assigning to r-value/temporary' warning, since test_func() isn't returning by reference.
 
Also, test_func(void) should be test_func(), no need for the 'void' there. I don't know if a warning will result. Probably something like "explicit void argument - compile with -ANSI to disable warning"
 

2. What would you expect the output to be if it compiled?

Undefined gibberish value - whatever 'static number v' initially resolves to, because it has never been assigned anything.
 

3. Now compare your results to what actually happens when you compile it. Is it what you expected?

Using GCC/MinGW 4.7.2:
 
I didn't get the warning I expected on assigning "test_func() = one;",
instead I got an *error* on on the member variable assignment version: "test_func().x += 1.0f;"
 
error: using temporary as lvalue [-fpermissive]
 
 
 
I only found out yesterday that this is valid and standardized C++:
const int &refToTemp = 357;
...it just only lasts to the end of the scope that the expression is contained in. Still it's useful for avoiding a copy in some circumstances, which is why I looked it up:
//Only makes a copy if 'condition' is false.
const std::string &myString = ( ...condition... ? this->memberString : this->GetCopyOfSubStr_ReturnByValue());
this->UseString(myString);

#3Servant of the Lord

Posted 26 January 2013 - 09:31 AM

Apparently GCC catches it also. Here's my expected results before compiling and before reading others' comments:

1. Without using a compiler look at the code. Would you expect any warnings or errors from the compiler? Why?

"test_func() = one;"- Some kind of 'Assigning to r-value/temporary' warning, since test_func() isn't returning by reference.
 
Also, test_func(void) should be test_func(), no need for the 'void' there. I don't know if a warning will result. Probably something like "explicit void argument - compile with -ANSI to disable warning"
 

2. What would you expect the output to be if it compiled?

Undefined gibberish value - whatever 'static number v' initially resolves to, because it has never been assigned anything.
 

3. Now compare your results to what actually happens when you compile it. Is it what you expected?

Using GCC/MinGW 4.7.2:
 
I didn't get the warning I expected on assigning "test_func() = one;",
instead I got an *error* on on the member variable assignment version: "test_func().x += 1.0f;"
 
error: using temporary as lvalue [-fpermissive]
 
 
 
I only found out yesterday that this is valid and standardized C++:
const int &refToTemp = 357;
...it just only lasts to the end of the scope that the expression is contained in, still it's useful for avoiding a copy in some circumstances, which is why I looked it up.
//Only makes a copy if 'condition' is false.
const std::string &myString = ( ...condition... ? this->memberString : this->GetCopyOfSubStr_ReturnByValue());
this->UseString(myString);

#2Servant of the Lord

Posted 26 January 2013 - 09:29 AM

Apparently GCC catches it also. Here's my expected results before compiling and before reading others' comments:

 

 

1. Without using a compiler look at the code. Would you expect any warnings or errors from the compiler? Why?

"test_func() = one;"- Some kind of 'Assigning to r-value/temporary' warning, since test_func() isn't returning by reference.
 
Also, test_func(void) should be test_func(), no need for the 'void' there. I don't know if a warning will result. Probably something like "explicit void argument - compile with -ANSI to disable warning"
 

2. What would you expect the output to be if it compiled?

Undefined gibberish value - whatever 'static number v' initially resolves to, because it has never been assigned anything.
 

3. Now compare your results to what actually happens when you compile it. Is it what you expected?

Using GCC/MinGW 4.7.2:
 
I didn't get the warning I expected on assigning "test_func() = one;",
instead I got an *error* on on the member variable assignment version: "test_func().x += 1.0f;"
 
error: using temporary as lvalue [-fpermissive]
 
 
 
 
I only found out yesterday that this is valid and standardized C++:
const int &refToTemp = 357;
 
...it just only lasts to the end of the scope that the expression is contained in, still it's useful for avoiding a copy in some circumstances, which is why I looked it up.
//Only makes a copy if 'condition' is false.
const std::string &myString = ( ...condition... ? this->memberString : this->GetCopyOfSubStr());
this->UseString(myString);

#1Servant of the Lord

Posted 26 January 2013 - 09:24 AM

Apparently GCC catches it also. Here's my expected results before compiling and before reading others' comments:

 

 

1. Without using a compiler look at the code. Would you expect any warnings or errors from the compiler? Why?

"test_func() = one;"- Some kind of 'Assigning to r-value/temporary' warning, since test_func() isn't returning by reference.
 
Also, test_func(void) should be test_func(), no need for the 'void' there. I don't know if a warning will result. Probably something like "explicit void argument - compile with -ANSI to disable warning"
 

2. What would you expect the output to be if it compiled?

Undefined gibberish value - whatever 'static number v' initially resolves to, because it has never been assigned anything.
 

3. Now compare your results to what actually happens when you compile it. Is it what you expected?

Using GCC/MinGW 4.7.2:
 
I didn't get the warning I expected on assigning "test_func() = one;",
instead I got an *error* on on the member variable assignment version: "test_func().x += 1.0f;"
 
error: using temporary as lvalue [-fpermissive]

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