Unexpected behavior when using algorithm::trim() to remove spaces

[rosenrodt]

The issue comes from boostorg/compute#817 where boost::trim() is invoked to sanitize OpenCL kernel arguments from preprocessor-generated strings. One of the failing cases taken directly from the boost compute repo is this:

two, pi          // original string   
[two, pi]        // vector after split() using comma as delimiter
two              // first element after trim()
 p               // second element after trim()

Here the trim() actually leave a leading space left of pi and slices one valid character on the right. One big BUT: this only happens to Linux cross-compiler targeting Android platform, downloaded from Android NDK page. Where as MSVC on Windows, GCC/Clang on Mac all run without problems. What might be the reason of this unexpected behavior?

[mclow]

Since you didn't provide an actual test program, I wrote my own:

#include <iostream>
#include <boost/algorithm/string/split.hpp>
#include <boost/algorithm/string/trim.hpp>

namespace ba = boost::algorithm;

int main ()
{
	std::string s("two, pi");
	std::vector<std::string> v;
	ba::split(v, s, ba::is_any_of(","));
	for (auto const &st : v) 
		std::cout << "'" << st << "'" << std::endl;
	std::cout << "-----" << std::endl;
	for (auto st : v)
	{
		ba::trim(st);
		std::cout << "'" << st << "'" << std::endl;
	}
}

$ clang++ -std=c++14 -I $BOOST boost.cpp && ./a.out 
'two'
' pi'
-----
'two'
'pi'

That looks fine to me.

One big BUT: this only happens to Linux cross-compiler targeting Android platform, downloaded from Android NDK page

Can you run this program on your platform and tell me what happens? Also, what version of Boost are you using?

[rosenrodt]

Thanks! That I did not providing a minimal example was lazy on my part.

Here is the result of the test program you provided:

export compile=/mnt/d/tools/android/android_toolchain_linux/bin/aarch64-linux-android-clang++

$ $compile -std=c++14 -I /mnt/d/repo/boost_1_68_0 src/test.cpp
$ adb push a.out data/local && adb shell ./data/local/a.out
a.out: 1 file pushed. 8.8 MB/s (223432 bytes in 0.024s)
'two'
' pi'
-----
'two'
' p'

The Boost version I have is 1.68.0. Compiled with Android cross compiler under Windows Linux Subsystem

[mclow]

The only difference that I can see is that you're using Boost 1.68.0, and I'm using trunk. However, I don't think that code has changed since before 1.68.0 (checks - nope)

That's very odd. And the fact that it only fails when cross-compiling to ARM suggests a tool problem. Doesn't rule out a bug in Boost, though.