Ubuntu上的gcc問題與數學庫的窗口上的Bash

我有一個使用「-lm」標誌來包含數學庫的makefile。我還爲每個.c文件包含#include。我仍然收到數學錯誤和「未定義的參考」，如exp，floor和pow等Ubuntu上的gcc問題與數學庫的窗口上的Bash

在windows Ubuntu上使用bash。

複製我的終端輸出的：

[email protected]:~/software/BICseq2/NBICseq-norm_v0.2.4$ make 
gcc -g -O2 -Wall -lm -c -o combineFile/combine.o combineFile/combine.c 
gcc -g -O2 -Wall -lm -c -o lib/read.o lib/read.c 
lib/read.c: In function ‘read_table’: 
lib/read.c:74:14: warning: variable ‘flag’ set but not used [-Wunused-but-set-variable] 
    int i=0,j=0,flag=1,low_mmry = 40000, is_num=0,k; 
      ^
gcc -g -O2 -Wall -lm combineFile/combine.o lib/read.o -o combineFile/combineFile 
gcc -g -O2 -Wall -lm -c -o DataPrepare/DtaPrep.o DataPrepare/DtaPrep.c 
gcc -g -O2 -Wall -lm -c -o lib/statlib.o lib/statlib.c 
gcc -g -O2 -Wall -lm DataPrepare/DtaPrep.o lib/read.o lib/statlib.o -o DataPrepare/PrepPois 
DataPrepare/DtaPrep.o: In function `print_oneline': 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/DataPrepare/DtaPrep.c:593: undefined reference to `pow' 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/DataPrepare/DtaPrep.c:591: undefined reference to `log' 
DataPrepare/DtaPrep.o: In function `calculate_bias': 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/DataPrepare/DtaPrep.c:685: undefined reference to `pow' 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/DataPrepare/DtaPrep.c:690: undefined reference to `exp' 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/DataPrepare/DtaPrep.c:681: undefined reference to `log' 
DataPrepare/DtaPrep.o: In function `fprint_gc_bin': 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/DataPrepare/DtaPrep.c:810: undefined reference to `floor' 
DataPrepare/DtaPrep.o: In function `fprintf_predicted': 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/DataPrepare/DtaPrep.c:850: undefined reference to `exp' 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/DataPrepare/DtaPrep.c:860: undefined reference to `floor' 
DataPrepare/DtaPrep.o: In function `calculate_bias': 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/DataPrepare/DtaPrep.c:749: undefined reference to `exp' 
lib/statlib.o: In function `db_shuffle': 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/lib/statlib.c:56: undefined reference to `floor' 
lib/statlib.o: In function `db_shuffle_int': 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/lib/statlib.c:71: undefined reference to `floor' 
lib/statlib.o: In function `rgamma1': 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/lib/statlib.c:99: undefined reference to `log' 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/lib/statlib.c:100: undefined reference to `pow' 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/lib/statlib.c:103: undefined reference to `pow' 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/lib/statlib.c:104: undefined reference to `exp' 
/home/labyu/software/BICseq2/NBICseq-norm_v0.2.4/lib/statlib.c:90: undefined reference to `log' 
collect2: error: ld returned 1 exit status 
make: *** [PrepPois] Error 1

但是，當我做的一個範例程序，比如這個：test.c的

#include <stdio.h> 
#include <math.h> 

int main(void) 
{ 
    int number; 
    number = pow(10,2); 
    printf("%d\n", number); 
    return 0; 
}

我可以用gcc test.c的，即使沒有-lm標誌，它編譯得很好。

這是一個錯誤？

來源

2016-08-12 odoland

把旗子後所有對象連接 – FreeStyle4

檢查[\ [this \]]（http://stackoverflow.com/q/ 19508136/1620779）類似的問題。 – sjsam

@cxw'-lm'標誌在你的命令行中是無用的，這是一條編譯行。 –

在您的測試情況下，因爲所有的數據是不變的，它似乎編譯器計算直接的價值（也可能取決於編譯器，但最近的gcc版本似乎處理這個罰款）

拆卸時碼（86），我們清楚地看到它通過在該線下方

d: c7 45 fc 64 00 00 00 movl $0x64,-0x4(%rbp) 
    14: 8b 45 fc    mov -0x4(%rbp),%eax 
    17: 89 c2     mov %eax,%edx 
    19: 48 8d 0d 00 00 00 00 lea 0x0(%rip),%rcx  # 20 <main+0x20> 
    20: e8 00 00 00 00   callq 25 <main+0x25> 
    25: b8 00 00 00 00   mov $0x0,%eax 
    2a: 90      nop 
    2b: 48 83 c4 30    add $0x30,%rsp 
    2f: 5d      pop %rbp 
    30: c3      retq 
    31: 90      nop

給printf

0: 55      push %rbp 
    1: 48 89 e5    mov %rsp,%rbp 
    4: 48 83 ec 30    sub $0x30,%rsp 
    8: e8 00 00 00 00   callq d <main+0xd>

直接值100我已經改變了代碼如下：

#include <stdio.h> 
#include <math.h> 

int main(void) 
{ 
    int number; 
    int v=10; 
    number = pow(v,2); 
    printf("%d\n", number); 
    return 0; 
}

，現在當我處的文件獲得：

>nm simplemath.o 
0000000000000000 b .bss 
0000000000000000 d .data 
0000000000000000 p .pdata 
0000000000000000 r .rdata 
0000000000000000 r .rdata$zzz 
0000000000000000 t .text 
0000000000000000 r .xdata 
       U __main 
0000000000000000 T main 
       U pow 
       U printf

之前我介紹了變量，則pow符號並沒有提及。編譯器靜態地完成了數學。

反彙編顯示更復雜的代碼，使用浮點寄存器和所有。

0000000000000000 <main>: 
    0: 55      push %rbp 
    1: 48 89 e5    mov %rsp,%rbp 
    4: 48 83 ec 40    sub $0x40,%rsp 
    8: e8 00 00 00 00   callq d <main+0xd> 
    d: c7 45 fc 0a 00 00 00 movl $0xa,-0x4(%rbp) 
    14: 66 0f ef c0    pxor %xmm0,%xmm0 
    18: f2 0f 2a 45 fc   cvtsi2sdl -0x4(%rbp),%xmm0 
    1d: 48 b8 00 00 00 00 00 movabs $0x4000000000000000,%rax 
    24: 00 00 40 
    27: 48 89 45 e8    mov %rax,-0x18(%rbp) 
    2b: f2 0f 10 4d e8   movsd -0x18(%rbp),%xmm1 
    30: e8 00 00 00 00   callq 35 <main+0x35> <== the linker wil add the call to pow here 
    35: f2 0f 2c c0    cvttsd2si %xmm0,%eax 
    39: 89 45 f8    mov %eax,-0x8(%rbp) 
    3c: 8b 45 f8    mov -0x8(%rbp),%eax 
    3f: 89 c2     mov %eax,%edx 
    41: 48 8d 0d 00 00 00 00 lea 0x0(%rip),%rcx  # 48 <main+0x48> 
    48: e8 00 00 00 00   callq 4d <main+0x4d> 
    4d: b8 00 00 00 00   mov $0x0,%eax 
    52: 90      nop 
    53: 48 83 c4 40    add $0x40,%rsp 
    57: 5d      pop %rbp 
    58: c3      retq

但令我驚訝的是，不需要-lm，它沒有它的鏈接。最新的gcc版本必須默認包含它，因爲它經常被使用。也許有人可以證實。你的版本似乎需要它，我的沒有（海灣合作委員會4.9.4）

來源

2016-08-12 20:00:09

Ubuntu上的gcc問題與數學庫的窗口上的Bash

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