opencv在交叉編譯的時候的一些常見報錯和處理---How to use std::stoul and std::stoull in Android?
How to use std::stoul and std::stoull in Android?
Ask Question Asked 8 years, 7 months ago Modified 6 years, 2 months ago Viewed 13k times 22C++11 has two new string conversion functions into unsigned long
and long long
: std::stoul()
and std::stoll()
.
The recent Android NDK r9 introduces Clang 3.3 compiler which is said to be C++11 feature complete. There are prototypes for these functions deep inside NDK, however I cannot use them.
What do I need to do to use them?
P.S. I already do LOCAL_CPPFLAGS += -std=c++11
2 Answers
The reason why you cannot use the functions is quite deep rooted, and unfortunately currently unsolvable.
Looking into the libs/armeabi-v7a/include/bits/c++config.h
file in the gnu stdlibc++ folder, you'll see this:
...
/* Define if C99 functions or macros from <wchar.h>, <math.h>, <complex.h>,
<stdio.h>, and <stdlib.h> can be used or exposed. */
/* #undef _GLIBCXX_USE_C99 */
...
The above, in conjunction with the following snippet from bits/basic_string.h
spells bad news:
...
#if (defined(__GXX_EXPERIMENTAL_CXX0X__) && defined(_GLIBCXX_USE_C99) \
&& !defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF))
/* The definitions of Numeric Conversions [string.conversions] */
#endif
...
Thus, these functions are unusable in the NDK.
Root Cause: The root cause seems to be that the C99 functionality usage has been disabled in the GNU stdlibc++ on the armeabi-v7a platform due to the fact the the Bionic libc does not support complex math (the standard C library on Android is Bionic).
Possible Fix (untested): Explore CrystaX's Android NDK which seems to have extensions over the Vanilla Android NDK.
Note: __GXX_EXPERIMENTAL_CXX0X__
is defined by adding -std=gnu++11
to APP_CXXFLAGS
or LOCAL_CXXFLAGS
Detailed Test log: Built using NDK version r8e
jni/Application.mk:
APP_STL := gnustl_static
APP_CXXFLAGS += -std=gnu++11
NDK_TOOLCHAIN_VERSION := 4.7
jni/Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := cxx11
LOCAL_SRC_FILES := cxx11.cpp
include $(BUILD_EXECUTABLE)
jni/cxx11.cpp:
#include <iostream>
#include <string>
int main(int argc, char* argv[]) {
#if defined(__GXX_EXPERIMENTAL_CXX0X__)
std::cout<<"__GXX_EXPERIMENTAL_CXX0X__ defined."<<std::endl;
#else
std::cout<<"__GXX_EXPERIMENTAL_CXX0X__ not defined."<<std::endl;
#endif
#if defined(_GLIBCXX_USE_C99)
std::cout<<"_GLIBCXX_USE_C99 defined."<<std::endl;
#else
std::cout<<"_GLIBCXX_USE_C99 not defined."<<std::endl;
#endif
#if defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF)
std::cout<<"_GLIBCXX_HAVE_BROKEN_VSWPRINTF defined."<<std::endl;
#else
std::cout<<"_GLIBCXX_HAVE_BROKEN_VSWPRINTF not defined."<<std::endl;
#endif
#if (defined(__GXX_EXPERIMENTAL_CXX0X__) && defined(_GLIBCXX_USE_C99) \
&& !defined(_GLIBCXX_HAVE_BROKEN_VSWPRINTF))
std::string s="1";
std::cout<<"ll:"<<std::stoll(s)<<std::endl<<"ul:"<<std::stoul(s)<<std::endl;
#else
std::cout<<"No support for stoll/stoul."<<std::endl;
#endif
return(0);
}
Output on Nexus 4 (Android 4.3):
u0_a51@mako:/ $ /data/local/tmp/cxx11
__GXX_EXPERIMENTAL_CXX0X__ defined.
_GLIBCXX_USE_C99 not defined.
_GLIBCXX_HAVE_BROKEN_VSWPRINTF not defined.
No support for stoll/stoul.
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edited Aug 8, 2013 at 12:59
answered Aug 8, 2013 at 11:16
Samveen
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- Any chance to replace stdlib? – Sergey K. Aug 8, 2013 at 11:19
- @SergeyK. Try CrystaX's Android NDK, which seems to have some fixes over the Vanilla Android NDK. I am looking to explore it as well. – Samveen Aug 8, 2013 at 11:43
- Have you tried NDK r9? Maybe we can define _GLIBCXX_USE_C99 manually? – Sergey K. Aug 8, 2013 at 11:44
-
@SergeyK. Naah. Already tried
LOCAL_CFLAGS := -D _GLIBCXX_USE_C99=1
. It's a very deep-rooted problem. – Samveen Aug 8, 2013 at 11:46 - Ok, this seems to be a great answer. – Sergey K. Aug 8, 2013 at 12:17
Adding:
APP_STL := c++_static
to Application.mk fixed my issue of not being able to access std::stoi() (using gcc 4.8.4).
solution via Daniel Tavares, from this Google Groups post.
Share answered Dec 29, 2015 at 0:40 Mark S. 7111 silver badge33 bronze badges-
Did this also fix the issue of access to the
unsigned long
andlong long
variants of the functions(stoul
andstoll
)? – Samveen Feb 22, 2016 at 5:14 - That solution helped me with stoul(). Thanks. – Stranger May 5, 2017 at 16:18
-stdlib=libc++ -std=c++11
for the LOCAL_CFLAGS) – FDinoff Jul 30, 2013 at 15:24-std=c++11
– Sergey K. Jul 30, 2013 at 16:01-stdlib=libc++
is also needed make sure you try it – aaronman-E
to show the preprocessor output you can see thatbits/basic_string.h
is included and that appears to be wherestoll
is defined howeverstoll
does not appear in the preprocessor output. – FDinoff Jul 30, 2013 at 18:50