gcc -O3 标志导致 -Winline "调用不太可能,代码大小会增长"警告

gcc -O3 flag causes -Winline "call is unlikely and code size would grow" warning

本文关键字:代码 警告 标志 -O3 -Winline gcc 调用      更新时间:2023-10-16

我在Ubuntu 14.04和gcc 4.9.3上。我遇到了一个奇怪的问题,当我启用O3优化时,会弹出一些"调用不太可能,代码大小会增长[-Weror=inline]"错误。我的代码中没有内联关键字。为什么gcc会对代码进行内联优化,从而触发自己的警告?

显然,禁用Winline会编译,但有更好的方法来解决这个问题吗?

我正在使用的库是Point Cloud库,为了完整起见,代码如下所示。

我的CMakeLists

cmake_minimum_required(VERSION 2.8)
project(Test)
set(PROJECT_SRCS
${PROJECT_SOURCE_DIR}/Test.cpp
)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -W -Werror -Winline")
# causes error
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -O3")
find_package( PCL 1.7 REQUIRED )
include_directories(${PCL_INCLUDE_DIRS})
add_executable(${PROJECT_NAME} ${PROJECT_SRCS})
target_link_libraries(${PROJECT_NAME} ${PCL_LIBRARIES})

测试.cpp

#include <string>
#include <vector>
#include "pcl/common/common_headers.h"
#include "pcl/io/obj_io.h"
#include "pcl/io/ply_io.h"
#include "pcl/io/vtk_lib_io.h"
#include "pcl/visualization/pcl_visualizer.h"
int main(){
  pcl::TextureMesh mesh;
  pcl::PointCloud<pcl::PointNormal> xyz;
  pcl::PointNormal point1;
  pcl::PointNormal point2;
  pcl::PointNormal point3;
  point1.x = 0;
  point2.x = 1;
  point3.x = 0;
  point1.y = 0;
  point2.y = 0;
  point3.y = 1;
  point1.z = 2;
  point2.z = 2;
  point3.z = 2;
  xyz.push_back(point1);
  xyz.push_back(point2);
  xyz.push_back(point3);
  pcl::toPCLPointCloud2(xyz, mesh.cloud);
  std::vector<pcl::Vertices> mesh_poly;
  std::vector<Eigen::Vector2f, Eigen::aligned_allocator<Eigen::Vector2f> > mesh_tex;
  pcl::TexMaterial mesh_material;
  pcl::Vertices v;
  v.vertices.push_back(0);
  v.vertices.push_back(1);
  v.vertices.push_back(2);
  mesh_poly.push_back(v);
  Eigen::Vector2f tex1;
  Eigen::Vector2f tex2;
  Eigen::Vector2f tex3;
  tex1(0) = -1.0;
  tex1(1) = 0.0;
  tex2(0) = -1.0;
  tex2(1) = 1.0;
  tex3(0) = 2.0;
  tex3(1) = 0.0;
  mesh_tex.push_back(tex1);
  mesh_tex.push_back(tex2);
  mesh_tex.push_back(tex3);
  mesh_material.tex_file = "lena.png";
  mesh_material.tex_name = "material_0";
  mesh.tex_polygons.push_back(mesh_poly);
  mesh.tex_coordinates.push_back(mesh_tex);
  mesh.tex_materials.push_back(mesh_material);
  pcl::io::saveOBJFile("out.obj", mesh);
  return 0;
}

编辑:更新错误消息

In file included from /usr/local/include/pcl-1.8/pcl/io/obj_io.h:40:0,
                 from /home/david/test/Test.cpp:5:
/usr/local/include/pcl-1.8/pcl/TextureMesh.h: In function ‘int main()’:
/usr/local/include/pcl-1.8/pcl/TextureMesh.h:50:10: error: inlining failed in call to ‘pcl::TexMaterial::~TexMaterial()’: call is unlikely and code size would grow [-Werror=inline]
   struct TexMaterial
          ^
/home/david/test/Test.cpp:37:20: error: called from here [-Werror=inline]
   pcl::TexMaterial mesh_material;
                ^
In file included from /usr/local/include/pcl-1.8/pcl/io/obj_io.h:40:0,
                 from /home/david/test/Test.cpp:5:
/usr/local/include/pcl-1.8/pcl/TextureMesh.h:91:10: error: inlining     failed in call to ‘pcl::TextureMesh::~TextureMesh()’: call is unlikely and code size would grow [-Werror=inline]
   struct TextureMesh
          ^
/home/david/test/Test.cpp:14:20: error: called from here [-Werror=inline]
   pcl::TextureMesh mesh;
                    ^
In file included from /usr/local/include/pcl-1.8/pcl/io/obj_io.h:40:0,
             from /home/david/test/Test.cpp:5:
/usr/local/include/pcl-1.8/pcl/TextureMesh.h:50:10: error: inlining failed in call to ‘pcl::TexMaterial::~TexMaterial()’: call is unlikely and code size would grow [-Werror=inline]
   struct TexMaterial
          ^
/home/david/test/Test.cpp:37:20: error: called from here [-Werror=inline]
   pcl::TexMaterial mesh_material;
                    ^
In file included from /usr/local/include/pcl-1.8/pcl/io/obj_io.h:40:0,
             from /home/david/test/Test.cpp:5:
/usr/local/include/pcl-1.8/pcl/TextureMesh.h:91:10: error: inlining failed in call to ‘pcl::TextureMesh::~TextureMesh()’: call is unlikely and code size would grow [-Werror=inline]
   struct TextureMesh
          ^
/home/david/test/Test.cpp:14:20: error: called from here [-Werror=inline]
   pcl::TextureMesh mesh;
                ^
cc1plus: all warnings being treated as errors
make[2]: *** [CMakeFiles/Test.dir/Test.cpp.o] Error 1
make[1]: *** [CMakeFiles/Test.dir/all] Error 2
make: *** [all] Error 2

使用的类/结构可能具有内联成员,即使这在代码中不是显式的。

例如,pcl::TextureMesh结构将有一个隐式析构函数,根据C++标准:

隐式声明的析构函数是其类的内联公共成员。

看看这个,也考虑一下这个答案。

即使在-O3优化级别上没有inline关键字,GCC也会启用自动内联。因此,正如NathanOliver所说,PCL库中可能存在不太可能调用的代码(不幸的是,我不熟悉它)。我会将优化级别降低到-O2,或者禁用带有fno-inline-functions的主动内联

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