使用MSVC 2013正则表达式错误 [英] Regex error using MSVC 2013
问题描述
我有一块xml像代码来解析,在MSVC 2013中使用std :: regex
< GLVertex&
#version 450 core
layout(location = 0)in vec3 pos;
in VertexInfo {
vec2 uv;
} vertexInfo;
void main(){
gl_Position = vec4(pos,1.0);
vertexInfo.uv = pos.xy;
}
< GLVertex />
< GLFragment>
#version 450 core
layout(location = 0)uniform sampler2D g_map;
uniform uniform {
vec4 color;
};
layout(location = 0)out vec4 fragColor;
void main(){
fragColor = texture(g_map,vertexInfo.uv);
}
< GLFragment />
以下是模式:
< GLVertex>((。| \\\
)+)< GLVertex\ />
但程序总是崩溃!在我的正则表达式有任何错误?我在regex101测试。
PS。当我删除第五行:
vec2 uv;
它工作正常!
由于模式不高效,你会得到堆栈溢出(参数:0x00000001,0x00312FFC)
异常。我认为它是如何 std :: regex
处理重复的组(你已经定义一个 +
- 量化组(。| \\\
)。此模式匹配不是换行符(
)+ 。
)或换行符( \\\
)的每个字符,然后将该匹配存储在缓冲区中。然后,只有在调试模式中,才会发生迭代器调试问题。
std :: _ Orphan_Me
是发生断点的地方,在匹配字符串时,它被认为是最昂贵的方法。请参见
I have a piece of xml like code to parse, using std::regex in MSVC 2013
<GLVertex>
#version 450 core
layout(location = 0) in vec3 pos;
in VertexInfo{
vec2 uv;
}vertexInfo;
void main(){
gl_Position = vec4(pos, 1.0);
vertexInfo.uv = pos.xy;
}
<GLVertex/>
<GLFragment>
#version 450 core
layout(location = 0) uniform sampler2D g_map;
uniform Color {
vec4 color;
};
layout(location = 0) out vec4 fragColor;
void main(){
fragColor = texture(g_map, vertexInfo.uv);
}
<GLFragment/>
Here is the pattern:
<GLVertex>((.|\n)+)<GLVertex\/>
But the program always crash! Is there any bug in my regex? I've tested on regex101.
PS. when i delete the 5th line:
vec2 uv;
it works OK!
You get a Stack overflow (parameters: 0x00000001, 0x00312FFC)
exception as the pattern is not efficient. I think it is related to how std::regex
processes repeated groups (you have define one with a +
-quantifier group (.|\n)+
). This pattern matches each and every character that is not a newline (.
), or a newline (\n
), and then stores the match inside a buffer. Then, an issue with the iterator debugging happens only in Debug mode. The std::_Orphan_Me
is the place where the break occurs, and it is considered the most "expensive" method when matching strings. See performance killer -Debug Iterator Support in Visual studio
You should either switch to the Release mode, or test with a regex that does not require the use of the repeated groups, like any non-null character [^\x00]
with lazy quantifier *?
:
std::string str1 = "<GLVertex>\n#version 450 core\nlayout(location = 0) in vec3 pos;\nin VertexInfo{\n vec2 uv;\n}vertexInfo;\nvoid main(){\n gl_Position = vec4(pos, 1.0);\n vertexInfo.uv = pos.xy;\n}\n<GLVertex/>\n<GLFragment>\n#version 450 core\nlayout(location = 0) uniform sampler2D g_map;\nuniform Color {\n vec4 color;\n};\nlayout(location = 0) out vec4 fragColor;\nvoid main(){\n fragColor = texture(g_map, vertexInfo.uv);\n}\n<GLFragment/>";
std::regex reg1("<GLVertex>([^\\x00]*?)<GLVertex/>");
std::smatch find1;
if (std::regex_search(str1, find1, reg1)){
std::cout << find1[1].str();
}
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