Question about C++ feature (cout)

Reinhard · 2012-04-22 03:43

Hi, currently I test some C++ features.
I use the SimpleIDE Version 0.6.2. and have this code snippet

 #include <vector>
 #include <string>
 #include <iostream>
  using namespace std;

int main(void)
 {
     vector<unsigned char>v;     // ok
     v.push_back(0xAA);              // ok
      string s = "Hello";                  // ok
     cout << s << endl;              // Build failed here
      return 0;
 }

Get this build result

knoppix@Microknoppix:~/myC/propeller_chip/_propgcc/cpp_vector_test$ propeller-elf-c++ -o a.out -Os -mxmmc cpp_vector_test.c -s
/home/knoppix/propgcc/bin/../lib/gcc/propeller-elf/4.6.1/../../../../propeller-elf/lib/xmmc/libstdc++.a(basic_file.o): In function `.LVL34':
/home/steve/gcc/build/gcc/propeller-elf/xmmc/libstdc++-v3/src/basic_file.cc:219: undefined reference to `_fdopen'
collect2: ld returned 1 exit status

Can not copy the message from the Build Status window, so I reproduce it on command line, thats no diff.

Is it not planned to use cout on µC or do I something wrong or is it a bug ?

regards
Reinhard

Heater. · 2012-04-22 05:02

I suspect that cout and the streams "<<" require further library support (libstdc++) and that that library is huge, to big to think about fitting in the Prop.
It is hard enough getting printf and co. in there.

Reinhard · 2012-04-22 05:35

Yes, I see libstdc++ is a huge library and not needed for µCs like prop.But other objects like vectors can be used from STL, and this is a big advantage. (in xmm / xmmc models)

denominator · 2012-04-22 08:19

Reinhard wrote: »

Hi, currently I test some C++ features.
Is it not planned to use cout on µC or do I something wrong or is it a bug ?

Reinhard,

cout is supported in XMM/XMMC modes, so it's a bug. Feel free to file an issue on the PropGCC development website at http://code.google.com/p/propgcc/issues/list.

In the interim, you can work around this by including the following snippet of code somewhere (anywhere) in your program:

#include <stdio.h>
extern "C"
{
  FILE* fdopen(int fd, const char* mode) { printf("Ooops, if we got here there's trouble afoot\n"); }
}

Note that I haven't analyzed what that particular call to fdopen does (I believe the file in question is actually gcc/libstdc++-v3/config/io/basic_file_stdio.cc in the PropGCC source), but I know you don't need it for simple cout operations. With the above work-around, if you do something thta needs it, you'll get the "Ooops" error on your console.

Also note that adding iostream to a program adds around 500K, this it takes your 100K program and blows it up to over 600K! This takes almost a full minute to upload to a C3.

There is a "tiny" library posted on another thread at http://forums.parallax.com/showthread.php?139312-Tiny-I-O-Big-memory-savings-for-LMM-programs-that-print-get-from-the-serial-terminal; this would reduce your memory footprint greatly if you just want to print simple objects using cout (and not generic file I/O to memory, other devices, etc.).

Note, however, that the library was designed for LMM mode and I never tested it in XMM modes. Your issue caused me to finally test it; it appears there are some bugs and it doesn't work in XMM mode - I'll try to get to these soon. Watch the forum for updates.

- Ted

jazzed · 2012-04-23 11:39

Eric pushed a fix for the fdopen dependency. Thanks Eric.

A simple hello c++ cout program will work with board type C3 and -mxmm or -mxmm-split mode.
Unfortunately, -mxmmc model does not have enough data space in Propeller HUB RAM to run using cout.

Applications using the standard c++ library without cout and iostreams will run with -mxmmc programs.
You will need to use printf or some other console IO alternative of course.

I'll get some packages out soon. For binary users. Source builders can update and build now.

Thanks,
--Steve

Reinhard · 2012-04-23 12:40

Thank's to all be involved.I'll assert that if this issue run on C3, the propgcc (and the propeller) is in a liga like ARM.best regards,Reinhard

jazzed · 2012-04-23 14:14

Reinhard wrote: »

Thank's to all be involved.I'll assert that if this issue run on C3, the propgcc (and the propeller) is in a liga like ARM.best regards,Reinhard

Great! Hopefully we'll be able to add another ARM-like feature later :thumb:

Question about C++ feature (cout)

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