xC: build fails when optimization is turned off

[Endre]

Hi,

I am working on an USB CDC project. To get more verbose exception messages, I have turned optimization off. This caused build failure.
I have managed to reproduce it with AN00124_CDC_VCOM_class[2.0.2]:
Makefile:

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-XCC_FLAGS_U     = -Wall -O3 -report -DXUD_SERIES_SUPPORT=XUD_U_SERIES -g
+XCC_FLAGS_U     = -Wall -O0 -report -DXUD_SERIES_SUPPORT=XUD_U_SERIES -g

build error:

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Creating app_usb_cdc_demo_U.xe
../src/xud_cdc.xc: Error: Undefined reference to 'XUD_SetReady_In' (possible inline definition without external definition)
../src/xud_cdc.xc: Error: Undefined reference to 'XUD_SetReady_Out' (possible inline definition without external definition)
xmake[1]: *** [bin/U/app_usb_cdc_demo_U.xe] Error 1
xmake: *** [bin/U/app_usb_cdc_demo_U.xe] Error 2

My xTIMEcomposer Version: Community_14.1.2 (build 17961, Dec-04-2015)

[henk]

Hmm yes, I guess that the USB library is not designed to run without optimisation - it probably relies on it, in that it won't meet the real-time requirements of USB when compiled with different -O.

By the looks of it, to get it to compile you may have to remove the inline in front of those two functions, or add an externed one. But I don't know whether it will run correctly.

Cheers,
Henk

[Endre]

Hmm yes, I guess that the USB library is not designed to run without optimisation - it probably relies on it, in that it won't meet the real-time requirements of USB when compiled with different -O.

Hi,

I guess even if it doesn't work without optimization, it should compile.
I have never seen an ordinal C/C++ compiler which couldn't handle inline functions, defined in headers, without optimization.

[henk]

I completely agree with your sentiment. However compiling a tiny C program using a standard C compiler on my laptop disagrees with both of us:

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12:51:02 % cc t.c
Undefined symbols for architecture x86_64:
  "_f", referenced from:
      _main in t-04b1ce.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
12:51:04 % cc -O3 t.c
12:51:11 % 

Ie, this is the way C is; which is what XC follows closely. Arguably, the code should be written so that it does compile with and without optimisation. Something to be fixed.

For info, in the above code t.c contains the following:

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#include "a.h"

int main() {
  f();
  return 0;
}

a.h contains the following:

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inline void f() { }

I used LLVM version 7.3.0 (clang-703.0.29)

[Endre]

I completely agree with your sentiment. However compiling a tiny C program using a standard C compiler on my laptop disagrees with both of us

I have also tried with gcc:
hello.h:

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#ifndef _HELLO_H
#define _HELLO_H

#include <stdio.h>

inline void hello() {
	printf("hello\n");
}

#endif

hello.c:

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#include "hello.h"

int main(int argc, char ** argv) {
	hello();
	return 0;
}

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[endre@localhost InlineTest]$ gcc -O0 hello.c -o hello
[endre@localhost InlineTest]$ ./hello 
hello
[endre@localhost InlineTest]$ gcc --version
gcc (GCC) 4.8.3 20140911 (Red Hat 4.8.3-7)
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[endre@localhost InlineTest]$

This compile failure seems to be a clang "feature", maybe placing "static" before the "inline" would help (I haven't tried yet.)

[henk]

Yes - they behave differently.
The following line fixes it for Clang/xcc:

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extern void f();

in a file that includes the include file with the inline definitions.