vector and iterator problem

**BeBu** · 03-10-2009

Hi i got following code:

Code:

void STM32SPI::handleInterrupt() {
	if (SPI_I2S_GetITStatus(spiport, SPI_I2S_IT_TXE) == SET) {
		if (sendBufferPos != sendBuffer.end()) {
			SPI_I2S_SendData(spiport, *sendBufferPos);
			sendBufferPos++;
		} else {
			enableInterrupt(false);
			sendBuffer.clear();
		}
	}
	if (SPI_I2S_GetITStatus(spiport, SPI_I2S_IT_RXNE) == SET) {
		receiveBuffer.push_back((u8) SPI_I2S_ReceiveData(spiport));
	}
}

void STM32SPI::send() {
	sendBufferPos == sendBuffer.begin();
	enableInterrupt();
}

with sendBuffer and sendBufferPos beeing class members:

Code:

class STM32SPI{
	vector<u8>::iterator sendBufferPos;
	vector<u8> sendBuffer;
}

i am trying to do this:
after calling send the iterator is set to the begin of the vector and the interrupt is enabled, now everytime the interrupt handler is called, the iterator *should* move to
the next position till end(). but it doesnt. sendBufferPos != sendBuffer.end() is never true.
I am not touching the vector, so the iterator should not be invalidated as far as i know.

P.S.

the code is running on a microprocessor

**matsp** · 03-10-2009

I don't see anything wrong in your code. It may be either that the STL library is no working correctly, or the compiler decides that it doesn't need to change the variable outside of the function for some reason. Check the generated code, perhaps?

--
Mats

**adeyblue** · 03-10-2009

Code:

	sendBufferPos == sendBuffer.begin();

Are you sure you wanted comparison instead of assignment there?

**matsp** · 03-10-2009

Originally Posted by adeyblue

Code:

	sendBufferPos == sendBuffer.begin();

Are you sure you wanted comparison instead of assignment there?

Good spot!

@BeBu: You may want to raise the warning level - most compilers will warn for this sort of "code that doesn't do anything", and almost every time, the compiler is right in doing so.

--
Mats

**BeBu** · 03-11-2009

Yes thanks to both of you. That was it. Of course i didnt want a comparison but an assignement.

I turned all warning on and it got reported like statement value is not used.

**matsp** · 03-11-2009

Originally Posted by BeBu

I turned all warning on and it got reported like statement value is not used.

Yes, the exact wording is somewhat varying from compiler to compiler, but they usually have something in them to say "Do you really mean to do this meaningless stuff here, or did you mean something else?" Compiler warnings are USUALLY added for a reason, so it's a good idea to listen to them (and fix them) - there is nothing worse than compiling a piece of code that give 100 warnings, and then spend two days realizing that the code change you made added a 101st warning, that if you had seen the tree in the forest of warnings, you would have fixed it in 30 seconds.

A not so unusual one is "empty statement in if":

Code:

if (filePtr);
   printf("File opened OK");

Now, you'll scratch your head a bit before you figure out that the time you passed in a file that COULDN'T be opened, it still did the printf!

--
Mats

**Elkvis** · 03-11-2009

Originally Posted by matsp

Now, you'll scratch your head a bit before you figure out that the time you passed in a file that COULDN'T be opened, it still did the printf!
Mats

I've done exactly that before.... it took over a day to find it.

**matsp** · 03-11-2009

Originally Posted by Elkvis

I've done exactly that before.... it took over a day to find it.

Yes. It took several people 6 months to find that sort of thing in some obscure part of our embedded OS! They can be quite hard to find. If the compiler warns about it, you should be able fix it in 30 seconds.

--
Mats

**MarkZWEERS** · 03-11-2009

A not so unusual one is "empty statement in if":

Code:

if (filePtr);
   printf("File opened OK");

Now, you'll scratch your head a bit before you figure out that the time you passed in a file that COULDN'T be opened, it still did the printf!

Here's where a good editor like Emacs (in fact, only Emacs) proves its value: abscence of auto-indentation and coloring will tell you straight away that there's something wrong...
Microsoft Visual Studio never gave me that handy plus. Everybody, please use emacs :-)

**laserlight** · 03-11-2009

Originally Posted by MarkZWEERS

Here's where a good editor like Emacs (in fact, only Emacs) proves its value: abscence of auto-indentation and coloring will tell you straight away that there's something wrong...
Microsoft Visual Studio never gave me that handy plus.

Auto-indentation is a common enough feature that is present in Visual Studio as well, but it is the syntax highlighting that is more useful here since the code might not have been written by you.

**vart** · 03-11-2009

Originally Posted by MarkZWEERS

Microsoft Visual Studio never gave me that handy plus. Everybody, please use emacs :-)

Try

Ctrl+a, Alt+F8

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