如何为模板函数调用解释gcov结果

Question

问题1：如何解密函数名称，例如_ZN21CircularBufferManager4readIlEEmPT_m？ 我猜在那些长函数名（即l，t，h，d）中，“读取”之后的第二个字符必须与类型有关。 我使用unsigned char，unsigned short，signed long，double。

问题2：在第227行中，我看到16个分支。 为什么是16？ 另一方面，第222行有8个分支，这对我来说很有意义，因为2个状态（正确或错误）乘以4个函数将得出8个分支。

        -:  216:    template<typename Type>
function _ZN21CircularBufferManager4readIlEEmPT_m called 2 returned 100% blocks executed 63%
function _ZN21CircularBufferManager4readItEEmPT_m called 2 returned 100% blocks executed 50%
function _ZN21CircularBufferManager4readIhEEmPT_m called 10 returned 100% blocks executed 94%
function _ZN21CircularBufferManager4readIdEEmPT_m called 8 returned 100% blocks executed 94%
       22:  217:    uint32 read(Type* data, uint32 element_count)
        -:  218:    {
       22:  219:        uint32 size(sizeof(Type)*element_count);
        -:  220:
       22:  221:        uint32 write_pos_alias(this->write_pos);
       22:  222:        if (this->read_pos > this->write_pos) {
branch  0 taken 0% (fallthrough)
branch  1 taken 100%
branch  2 taken 0% (fallthrough)
branch  3 taken 100%
branch  4 taken 20% (fallthrough)
branch  5 taken 80%
branch  6 taken 13% (fallthrough)
branch  7 taken 88%
        3:  223:            write_pos_alias += this->allocated_size;
        -:  224:        }
        -:  225:        assert(write_pos_alias >= this->read_pos);
       22:  226:        uint32 n(write_pos_alias - this->read_pos); // number of bytes to reach the write position
       22:  227:        if (n==0 && this->stored_count==0) // <=> buffer is empty
branch  0 taken 50% (fallthrough)
branch  1 taken 50%
branch  2 taken 100% (fallthrough)
branch  3 taken 0%
branch  4 taken 0% (fallthrough)
branch  5 taken 100%
branch  6 never executed
branch  7 never executed
branch  8 taken 30% (fallthrough)
branch  9 taken 70%
branch 10 taken 0% (fallthrough)
branch 11 taken 100%
branch 12 taken 38% (fallthrough)
branch 13 taken 63%
branch 14 taken 0% (fallthrough)
branch 15 taken 100%
        -:  228:        {
        -:  229:            // no data read
        1:  230:            return 0;
        -:  231:        }
       21:  232:        else if (0<n && n<size) // read is stopped before read_pos crosses over write_pos.
branch  0 taken 100% (fallthrough)
branch  1 taken 0%
branch  2 taken 0% (fallthrough)
branch  3 taken 100%
branch  4 taken 100% (fallthrough)
branch  5 taken 0%
branch  6 taken 0% (fallthrough)
branch  7 taken 100%
branch  8 taken 70% (fallthrough)
branch  9 taken 30%
branch 10 taken 14% (fallthrough)
branch 11 taken 86%
branch 12 taken 63% (fallthrough)
branch 13 taken 38%
branch 14 taken 20% (fallthrough)
branch 15 taken 80%
        -:  233:        {
        2:  234:            return read(reinterpret_cast<uint8*>(data), n); //less data than required.
call    0 never executed
call    1 never executed
call    2 returned 100%
call    3 returned 100%
        -:  235:        }
        -:  236:        // It is guaranteed here and below that read_pos never crosses-over write_pos.
        -:  237:
       19:  238:        if (this->read_pos + size > this->allocated_size) // going beyond the end of buffer
branch  0 taken 0% (fallthrough)
branch  1 taken 100%
branch  2 taken 0% (fallthrough)
branch  3 taken 100%
branch  4 taken 11% (fallthrough)
branch  5 taken 89%
branch  6 taken 43% (fallthrough)
branch  7 taken 57%
        -:  239:        {
        4:  240:            uint32 n(this->allocated_size - this->read_pos); // number of bytes to reach the end of buffer
        -:  241:            return this->read(reinterpret_cast<uint8*>(data), n)
        4:  242:                 + this->read(reinterpret_cast<uint8*>(data)+n, size-n);
call    0 never executed
call    1 never executed
call    2 never executed
call    3 never executed
call    4 returned 100%
call    5 returned 100%
call    6 returned 100%
call    7 returned 100%
        -:  243:        }
       15:  244:        memcpy(reinterpret_cast<void*>(data), reinterpret_cast<void*>(this->buf+this->read_pos), size);
       15:  245:        incrementReadPos(size);
call    0 returned 100%
call    1 returned 100%
call    2 returned 100%
call    3 returned 100%
       15:  246:        return size;
        -:  247:    }

Answer 1

对于第一个问题，您可以通过c++filt命令将此输出通过管道传递，以使标识符脱散。

对于您的第二个问题，显然gcov不在乎错误是否被短路，它仍然通过三种方式来实现错误，而只有一种方式可以实现。

• true => n==0 && this->stored_count==0
• false => n!=0 && this->stored_count==0
• false => n!=0 && this->stored_count!=0
• false => n==0 && this->stored_count!=0

由于您以4种方式扩展了模板功能，因此共有16种。