SFML项目加载字体时出现Valgrind无效内存读取错误

问题现象 #

以下代码在加载SFML字体时，会触发Valgrind报告两个相同的无效读取错误：

// g++ sfml.cpp -o sfml_test -lsfml-graphics -lsfml-window -lsfml-system
#include <SFML/Graphics.hpp>
#include <iostream>

int main()
{
    sf::Font font;
    if (!font.loadFromFile("font.ttf"))
    {
        std::cout << "ruh oh" << std::endl;
    }

    sf::RenderWindow window(sf::VideoMode(200, 200), "SFML works!");

    return 0;
}

Valgrind错误输出示例：

==7557==  Invalid read of size 8
==7557==    at 0x401D734: strncmp (strcmp.S:175)
==7557==    by 0x400604D: is_dst (dl-load.c:209)
==7557==    by 0x4008566: _dl_dst_count (dl-load.c:246)
==7557==    by 0x4008757: expand_dynamic_string_token (dl-load.c:388)
==7557==    by 0x40088D1: fillin_rpath.isra.0 (dl-load.c:460)
==7557==    by 0x4008BE1: decompose_rpath (dl-load.c:631)
==7557==    by 0x4009745: cache_rpath (dl-load.c:673)
==7557==    by 0x4009745: cache_rpath (dl-load.c:654)
==7557==    by 0x4009745: _dl_map_object (dl-load.c:2074)
==7557==    by 0x400DDC0: openaux (dl-deps.c:64)
==7557==    by 0x4C0CACF: _dl_catch_exception (dl-error-skeleton.c:208)
==7557==    by 0x400E138: _dl_map_object_deps (dl-deps.c:248)
==7557==    by 0x4013DAA: dl_open_worker (dl-open.c:571)
==7557==    by 0x4C0CACF: _dl_catch_exception (dl-error-skeleton.c:208)
==7557==  Address 0x5a25719 is 9 bytes inside a block of size 15 alloc'd
==7557==    at 0x483877F: malloc (vg_replace_malloc.c:307)
==7557==    by 0x401C29A: strdup (strdup.c:42)
==7557==    by 0x4008B74: decompose_rpath (dl-load.c:606)
==7557==    by 0x4009745: cache_rpath (dl-load.c:673)
==7557==    by 0x4009745: cache_rpath (dl-load.c:654)
==7557==    by 0x4009745: _dl_map_object (dl-load.c:2074)
==7557==    by 0x400DDC0: openaux (dl-deps.c:64)
==7557==    by 0x4C0CACF: _dl_catch_exception (dl-error-skeleton.c:208)
==7557==    by 0x400E138: _dl_map_object_deps (dl-deps.c:248)
==7557==    by 0x4013DAA: dl_open_worker (dl-open.c:571)
==7557==    by 0x4C0CACF: _dl_catch_exception (dl-error-skeleton.c:208)
==7557==    by 0x40138F9: _dl_open (dl-open.c:837)
==7557==    by 0x545C257: dlopen_doit (dlopen.c:66)
==7557==    by 0x4C0CACF: _dl_catch_exception (dl-error-skeleton.c:208)

移除字体加载代码后，Valgrind不再报错。程序可正常执行，字体能成功加载使用。

环境信息 #

• 操作系统：PureOS 10（Debian分支）
• g++版本：(Debian 10.2.1-6) 10.2.1 20210110
• glibc版本：2.31
• SFML版本：2.5或2.6，可能通过sudo apt-get install libsfml-dev安装

解决方法 #

1. 使用Valgrind抑制文件（最简单方案） #

该错误源于glibc动态链接器处理rpath时的内存对齐问题，属于系统库层面的假阳性错误，不影响程序运行。可以创建抑制文件忽略这类错误：

• 创建抑制文件glibc-rpath.supp，内容如下：

{
   glibc_rpath_invalid_read
   Memcheck:Addr4
   Memcheck:Addr8
   fun:strncmp
   fun:is_dst
   fun:_dl_dst_count
   fun:expand_dynamic_string_token
   fun:fillin_rpath.isra.0
   fun:decompose_rpath
   fun:cache_rpath
   fun:_dl_map_object
   fun:openaux
   fun:_dl_catch_exception
   fun:_dl_map_object_deps
   fun:dl_open_worker
}
{
   glibc_rpath_invalid_read_2
   Memcheck:Addr4
   Memcheck:Addr8
   fun:strncmp
   fun:is_dst
   fun:_dl_dst_substitute
   fun:fillin_rpath.isra.0
   fun:decompose_rpath
   fun:cache_rpath
   fun:_dl_map_object
   fun:openaux
   fun:_dl_catch_exception
   fun:_dl_map_object_deps
   fun:dl_open_worker
}

• 运行Valgrind时指定抑制文件：

valgrind --suppress=glibc-rpath.supp ./sfml_test

2. 从源码编译静态链接的SFML #

Debian仓库的SFML可能依赖动态链接的系统库，导致触发rpath问题。自行编译静态链接的SFML可避免该问题：

• 安装编译依赖：

sudo apt-get install cmake libfreetype6-dev libx11-dev libxrandr-dev libudev-dev libopenal-dev libflac-dev libvorbis-dev libgl1-mesa-dev libegl1-mesa-dev

• 下载并编译SFML（以2.6.1版本为例）：

git clone https://github.com/SFML/SFML.git -b 2.6.1
cd SFML
mkdir build && cd build
cmake .. -DCMAKE_BUILD_TYPE=Release -DSFML_STATIC_LIBRARIES=ON
make -j$(nproc)
sudo make install

• 编译程序时使用静态链接：

g++ sfml.cpp -o sfml_test -static -lsfml-graphics-s -lsfml-window-s -lsfml-system-s -lfreetype -lX11 -lXrandr -ludev -lopenal -lflac -lvorbis -lGL -lEGL

3. 升级glibc或Valgrind #

该错误是glibc 2.31与Valgrind 3.16.1的兼容性问题，升级到更新版本的glibc（2.32+）或Valgrind（3.18+）可解决。不过PureOS 10为稳定版，升级可能需要手动编译或添加第三方源。

内容的提问来源于stack exchange，提问作者Momus