Question

我正在对树结构进行插入/搜索，但在释放内存时遇到了问题。当我在return语句之前的代码末尾添加“ delete currentNode”时，在运行后不久我会遇到此错误：

library("plm" )
library(RStata)
data("Cigar", package = "plm")
z <- Cigar[ Cigar$year %in% c( 63, 73) , ]

options("RStata.StataPath" = "\"C:\\Program Files (x86)\\Stata14\\StataSE-64\"")
options("RStata.StataVersion" = 14)

# Stata fe 
stata_do1 <- '
  xtset state year
  xtreg sales pop, fe
'
stata(stata_do1, data.out = TRUE, data.in = z)
#> . 
#> .   xtset state year
#>        panel variable:  state (strongly balanced)
#>         time variable:  year, 63 to 73, but with gaps
#>                 delta:  1 unit
#> .   xtreg sales pop, fe
#> 
#> Fixed-effects (within) regression               Number of obs     =         92
#> Group variable: state                           Number of groups  =         46
#> 
#> R-sq:                                           Obs per group:
#>      within  = 0.0118                                         min =          2
#>      between = 0.0049                                         avg =        2.0
#>      overall = 0.0048                                         max =          2
#> 
#>                                                 F(1,45)           =       0.54
#> corr(u_i, Xb)  = -0.3405                        Prob > F          =     0.4676
#> 
#> ------------------------------------------------------------------------------
#>        sales |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
#> -------------+----------------------------------------------------------------
#>          pop |  -.0032108   .0043826    -0.73   0.468    -.0120378    .0056162
#>        _cons |   141.5186   18.06909     7.83   0.000     105.1256    177.9116
#> -------------+----------------------------------------------------------------
#>      sigma_u |  34.093409
#>      sigma_e |  15.183908
#>          rho |  .83448264   (fraction of variance due to u_i)
#> ------------------------------------------------------------------------------
#> F test that all u_i=0: F(45, 45) = 8.91                      Prob > F = 0.0000

# R 
z2 <- pdata.frame( z , index=c("state", "year")  )    
coef( plm( sales ~ pop , data= z2  , model="within" ) )
#>          pop 
#> -0.003210817

# Stata re
stata_do2 <- '
  xtset state year
  xtreg sales pop, re
'
stata(stata_do2, data.out = TRUE, data.in = z)
#> . 
#> .   xtset state year
#>        panel variable:  state (strongly balanced)
#>         time variable:  year, 63 to 73, but with gaps
#>                 delta:  1 unit
#> .   xtreg sales pop, re
#> 
#> Random-effects GLS regression                   Number of obs     =         92
#> Group variable: state                           Number of groups  =         46
#> 
#> R-sq:                                           Obs per group:
#>      within  = 0.0118                                         min =          2
#>      between = 0.0049                                         avg =        2.0
#>      overall = 0.0048                                         max =          2
#> 
#>                                                 Wald chi2(1)      =       0.40
#> corr(u_i, X)   = 0 (assumed)                    Prob > chi2       =     0.5257
#> 
#> ------------------------------------------------------------------------------
#>        sales |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
#> -------------+----------------------------------------------------------------
#>          pop |  -.0006838   .0010774    -0.63   0.526    -.0027955     .001428
#>        _cons |   131.1398   6.499511    20.18   0.000      118.401    143.8787
#> -------------+----------------------------------------------------------------
#>      sigma_u |  30.573218
#>      sigma_e |  15.183908
#>          rho |  .80214841   (fraction of variance due to u_i)
#> ------------------------------------------------------------------------------

# R random
coef(plm(sales ~ pop, 
            data=z, 
            model="random", 
            index=c("state", "year")))
#>   (Intercept)           pop 
#>  1.311398e+02 -6.837769e-04

当我不包括delete currentNode时，我的程序输出搜索结果的时间要比产生分段错误之前“删除”的时间长。我想知道我需要在哪里为currentNode分配内存，以便不会耗尽内存。

代码如下：

Error in `./a.out': double free or corruption

Answer 1

您正在为新的Node对象分配内存，但是永远不要使用它。相反，您立即使用指向root的指针覆盖了指向新对象的指针。调用delete currentNode时，您不会删除新对象，但是currentNode指向函数末尾的所有内容。

因此，不用写myEntry::Node *currentNode = new myEntry::Node;，只需写myEntry::Node *currentNode = root;。

这样，您无需分配任何内存，因此不必释放任何内存。

Answer 2

设置currentNode = root;时，将丢失对创建的新节点的引用，从而导致内存泄漏。

在哪里释放内存而不会导致错误

2 个答案: