我有一个基本的库，我用它来绘制 OpenGL 文本，每当我使用 valgrind 来确保它是气密的。我一直收到一个不寻常的错误，在我看来好像 linux c++ 库有问题。我想看看你们是否能发现我的错误或验证我所担心的，那就是我的 c++ 库有问题，需要更换。代码非常简单，但它同时使用了 OpenGL 和 FreeImage，因此某些行没有意义。

这里是 fontsystem.h:

#ifndef FONTSYSTEM_H
#define FONTSYSTEM_H

/*
    The Font System works by loading all the font images (max image size 32px^2) into memory and storing
  the OpenGL texture ID's into an array that can be access at all times. The DrawString() functions will
  search through the string for the specified character requested to draw and then it will draw a quad
  and paint the texture on it. Since all the images are pre-loaded, no loading of the images at load time
  is necessary, this is memory consuming but efficiant for the CPU. ALL functions WILL return a character
  string specifing errors or success. A function will work as long as it can and when an error happens,
  unless the error is fatal, the functions will NOT rollback changes! This ensures that during testing, a
  very certain bug can be spotted.
*/

#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string.h>
#include <assert.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glext.h>
#include <FreeImage.h>

#define REPORT(x) (std::cout<<x)
#define TIME clock()

class CFont
{
public:
    CFont();
    ~CFont();

    void DrawString(char *apString, int aiLetterSize, int aiX, int aiY);
    void DrawString(long anNumber, int aiLetterSize, int aiX, int aiY);
    void SetPath(char avPath[]);
    void SetupFont(); // This function will load as many images as possible into memory.

private:
    GLuint *mpTextIDs;
    int *mpDrawIDs;
    char *mpPath;

public:
    CFont(const CFont& a):
        mpTextIDs(a.mpTextIDs),
        mpDrawIDs(a.mpDrawIDs),
        mpPath(a.mpPath)
    {
        std::copy(a.mpTextIDs, a.mpTextIDs+128, mpTextIDs);
        std::copy(a.mpDrawIDs, a.mpDrawIDs+128, mpDrawIDs);
        std::copy(a.mpPath, a.mpPath + strlen(a.mpPath), mpPath);
    }

    CFont& operator=(const CFont& a)
    {
        GLuint *iTmpTex = new GLuint[128];
        int *iTmpDraw = new int[1024];
        char *vTmpPath = new char[4096];

        delete[] mpTextIDs;
        delete[] mpDrawIDs;
        delete[] mpPath;

        std::copy(a.mpTextIDs, a.mpTextIDs+128, iTmpTex);
        std::copy(a.mpDrawIDs, a.mpDrawIDs+128, iTmpDraw);
        std::copy(a.mpPath, a.mpPath + strlen(a.mpPath), vTmpPath);

        mpTextIDs = iTmpTex;
        mpDrawIDs = iTmpDraw;
        mpPath = vTmpPath;

        return *this;
    }
};

#endif // FONTSYSTEM_H

这里是 fontsystem.cpp:

#include "fontsystem.h"

CFont::CFont()
{
    mpTextIDs = new GLuint[128];
    mpDrawIDs = new int[1024];
    mpPath = new char[4096];
}

CFont::~CFont()
{
    delete[] mpTextIDs;
    delete[] mpDrawIDs;
    delete[] mpPath;
}

void CFont::DrawString(char *apString, int aiLetterSize, int aiX, int aiY)
{
    // Sanity check!
    if(apString == NULL)
    {
        REPORT("{Gfx}["<< TIME<< "]Error: Drawing string is NULL! <Font System>\n");
        return;
    }

    if(aiLetterSize <= 0)
    {
        REPORT("{Gfx}["<< TIME<< "]Error: Letter size is less than zero! <Font System>\n");
        return;
    }

    // Search the string from most significant character to least significant.
    int iSelectIndex = 0;
    int iNumOfSymb = 0;
    for(size_t i = 0; apString[i] != '\0'; ++i)
    {
        iSelectIndex = apString[i] >= '0' && apString[i] <= '9' ? (apString[i] - '0') :
                       apString[i] >= 'A' && apString[i] <= 'Z' ? (apString[i] - 'A' + 10) :
                       apString[i] >= 'a' && apString[i] <= 'z' ? (apString[i] - 'a' + 10) :
                       apString[i] == ' ' ? 36 : // This is a special case, This see's if the current character is a space or not.
                       -1;

        if(iSelectIndex == -1)
        {
            return;
        }

        // Add the current selected character to the drawing array.
        mpDrawIDs[i] = iSelectIndex;
        ++iNumOfSymb;
    }

    // Go through and draw each and every character.
    for(size_t i = 0; apString[i] != '\0'/*static_cast<size_t>(iNumOfSymb)*/; ++i)
    {
        // Paint each qaud with the X,Y coordinates. After each quad has been successfully drawn,
        // Add the size to the X coordinate. NOTE: Each character is square!!!

        glBindTexture(GL_TEXTURE_2D, mpTextIDs[(uint)apString[i]]);

        int yPos = apString[i] != 'q' || apString[i] != 'j' || apString[i] != 'y' ? aiY : aiY + (aiLetterSize/2);

        glBegin(GL_QUADS);
            glTexCoord2d(0, 0);
            glVertex2d(aiX, yPos);

            glTexCoord2d(1, 0);
            glVertex2d(aiX + aiLetterSize, yPos);

            glTexCoord2d(1, 1);
            glVertex2d(aiX + aiLetterSize, yPos + aiLetterSize);

            glTexCoord2d(0, 1);
            glVertex2d(aiX, yPos + aiLetterSize);
        glEnd();

        // Now, increase the X position by the size.
        aiX += aiLetterSize;
    }
}

void CFont::DrawString(long anNumber, int aiLetterSize, int aiX, int aiY)
{
    // Sanity Check!
    if(aiLetterSize <= 0)
    {
        REPORT("{Gfx}["<< TIME<< "]Error: Letter size is less than zero! <Font System>\n");
        return;
    }

    // Convert the supplied number to a character string via snprintf().
    char *vTempString = new char[1024];
    snprintf(vTempString, 1024, "%ld", anNumber);

    // Next, run DrawString().
    DrawString(vTempString, aiLetterSize, aiX, aiY);
}

void CFont::SetupFont()
{
    // First Load The PNG file holding the font.
    FreeImage_Initialise(false);

    FIBITMAP *spBitmap = FreeImage_Load(FIF_PNG, mpPath, BMP_DEFAULT);

    if(!spBitmap)
    {
        REPORT("{Gfx}["<< TIME<< "]Error: Was Unable to opne/decode font bitmap! <FreeImage>\n");
        return;
    }

    // Do an image sanity check.
    if(!FreeImage_HasPixels(spBitmap))
    {
        REPORT("{Gfx}["<< TIME<< "]Error: The font bitmap contains nothing! <FreeImage>\n");
        return;
    }

    // Retrieve all the image data from FreeImage.
    unsigned char *pData = FreeImage_GetBits(spBitmap);
    int iWidth = FreeImage_GetWidth(spBitmap);
    int iHeight = FreeImage_GetHeight(spBitmap);
    size_t const ciCharWidth = iHeight;
    size_t const ciCharHeight = iHeight;

    // Cutup the PNG.
    int iFontElementSize = (ciCharWidth*ciCharHeight)*4; // The first two numbers, are the dimensions fo the element, the last number (4) is the number of color channels (Red Green Blue and Alpha)
    unsigned char *pElemBuff = new unsigned char[iFontElementSize]; // The temporary element buffer.

    // Create all 37 OpenGL textures. 0-9 and A-Z and finally space (' ')
    glGenTextures(128, mpTextIDs);

    for (size_t iCharIdx = 0; 128 > iCharIdx; ++iCharIdx)
    {
        // Create character texture.
        size_t const ciScanOfst = ciCharWidth * iCharIdx * 4;
        for (size_t iScanLineIdx = 0; ciCharHeight > iScanLineIdx; ++iScanLineIdx)
        {
            memcpy(pElemBuff + ciCharWidth * iScanLineIdx * 4,
                   pData + ciScanOfst + iWidth * (ciCharHeight - iScanLineIdx - 1) * 4,
                   ciCharWidth * 4);
        }

        // Create The OpenGL Texture with the current Element.
        glBindTexture(GL_TEXTURE_2D, mpTextIDs[iCharIdx]);
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 32, 32, 0, GL_RGBA, GL_UNSIGNED_BYTE, pElemBuff);

        // Create the correct texture environment to the current texture.
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
        glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
    }

    // Do a little house cleaning!
    delete[] pElemBuff;
    FreeImage_Unload(spBitmap);
    FreeImage_DeInitialise();

    REPORT("{Gfx}["<< TIME<< "]Information: Font was created succesfully! <Font System>\n");
}

void CFont::SetPath(char avPath[])
{
    mpPath = avPath;
}

Valgrind 报告如下:

Starting the FontSystem...
FontSystem Started!
==5058== Invalid free() / delete / delete[] / realloc()
==5058==    at 0x402A8DC: operator delete[](void*) (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==5058==    by 0x8048F03: CFont::~CFont() (fontsystem.cpp:14)
==5058==    by 0x8048DE0: main (main.cpp:13)
==5058==  Address 0x804972f is not stack'd, malloc'd or (recently) free'd
==5058== 
==5058== 
==5058== HEAP SUMMARY:
==5058==     in use at exit: 4,172 bytes in 3 blocks
==5058==   total heap usage: 153 allocs, 151 frees, 135,457 bytes allocated
==5058== 
==5058== 20 bytes in 1 blocks are still reachable in loss record 1 of 3
==5058==    at 0x402A5E6: calloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==5058==    by 0x64DB3AD: _dlerror_run (dlerror.c:142)
==5058==    by 0x444EC64: ??? (in /usr/lib/libGL.so.295.59)
==5058== 
==5058== 56 bytes in 1 blocks are still reachable in loss record 2 of 3
==5058==    at 0x402BE68: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==5058==    by 0x442860E: ??? (in /usr/lib/libGL.so.295.59)
==5058==    by 0xBE872481: ???
==5058==    by 0x4E45504E: ???
==5058== 
==5058== 4,096 bytes in 1 blocks are definitely lost in loss record 3 of 3
==5058==    at 0x402B454: operator new[](unsigned int) (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==5058==    by 0x8048EAC: CFont::CFont() (fontsystem.cpp:7)
==5058==    by 0x8048D68: main (main.cpp:7)
==5058== 
==5058== LEAK SUMMARY:
==5058==    definitely lost: 4,096 bytes in 1 blocks
==5058==    indirectly lost: 0 bytes in 0 blocks
==5058==      possibly lost: 0 bytes in 0 blocks
==5058==    still reachable: 76 bytes in 2 blocks
==5058==         suppressed: 0 bytes in 0 blocks
==5058== 
==5058== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

我希望你们能帮我解决这个问题，因为这些似乎是我所有程序中的常见错误。作为一名编码员，我不太喜欢细微但令人讨厌的错误。

最佳答案

最突出的问题是这个:

==5058== Invalid free() / delete / delete[] / realloc()
==5058==    at 0x402A8DC: operator delete[](void*) (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==5058==    by 0x8048F03: CFont::~CFont() (fontsystem.cpp:14)
==5058==    by 0x8048DE0: main (main.cpp:13)
==5058==  Address 0x804972f is not stack'd, malloc'd or (recently) free'd
==5058== 

可以看到，它指的是fontsystem.cpp的第14行，在CFont的析构函数中，这里:

delete[] mpPath;

显然，您尝试delete [] 的内容从未动态分配过，或者未以正确的方式分配过。这个怎么可能？构造函数中的相应语句看起来不错:

mpPath = new char[4096];

所以 mpPath 的值一定是在调用构造函数后的某个地方发生了变化。确实有这个功能:

void CFont::SetPath(char avPath[])
{
    mpPath = avPath;
}

您可能在某处调用它，试图将堆栈分配的数组传输给它。你不应该那样做。如果 CFont 负责分配和释放，则不应有函数尝试获取外部数组并设置指向它的成员指针。考虑替代方案，例如将 avPath 数组复制到堆上新分配的数组中。并取消分配先前分配的一个。更好的是，使用 std::vector 或智能指针。

另一个问题是相关的:

==5058== 4,096 bytes in 1 blocks are definitely lost in loss record 3 of 3
==5058==    at 0x402B454: operator new[](unsigned int) (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==5058==    by 0x8048EAC: CFont::CFont() (fontsystem.cpp:7)
==5058==    by 0x8048D68: main (main.cpp:7)

这是与同一成员 mpPath 相关的内存泄漏。当然，这种泄漏的发生是因为 setPath 重置了指针而没有取消分配现有数组。同上问题。

其余消息与各种外部库调用有关。您可能无能为力的轻微内存泄漏。

关于c++ - 这个 valgrind 错误是什么意思？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13150955/