從gcc -o0優化級別鏈接錯誤

Question

我有一個項目，我正在嘗試做一些庫和系統調用基准測試。 我想確保編譯器不會優化我的調用。

這是我的makefile：

CC=gcc
CFLAGS= -I ./ 
LIBFLAGS= -lm
RM=/bin/rm -f

all:  osbench

osbench: osbench.c
    $(CC) $(CFLAGS) -o $@ osbench.c $(LIBFLAGS)

clean:
    $(RM) osbench *~

當我將標志設置為-o時，所有內容都會編譯並正常運行，但是我不確定編譯器是否忽略了對math.h庫的調用。 根據gcc手冊（ https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html）-o0表示不進行優化-這就是我想要的。 當我將標志設置為-o0時，會出現各種鏈接錯誤。

$(CC) $(CFLAGS) -o0 $@ osbench.c $(LIBFLAGS)

我還缺少另一個標志嗎？

gcc -I ./  -o0 osbench osbench.c -lm
osbench: In function `_fini':
(.fini+0x0): multiple definition of `_fini'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o:(.fini+0x0):                                 first defined here
osbench: In function `__data_start':
(.data+0x0): multiple definition of `__data_start'
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 0 has invalid symbol index 10
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 1 has invalid symbol index 11
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 2 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 3 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 4 has invalid symbol index 10
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 5 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 6 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 7 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 8 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 9 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 10 has invalid symbol index 11
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 11 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 12 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 13 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 14 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 15 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 16 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 17 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 18 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 19 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): reloca                                tion 20 has invalid symbol index 19
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.data+0x0):                                 first defined here
osbench: In function `__data_start':
(.data+0x8): multiple definition of `__dso_handle'
/usr/lib/gcc/x86_64-linux-gnu/4.6/crtbegin.o:(.data+0x0): first defined here
osbench:(.rodata+0x0): multiple definition of `_IO_stdin_used'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.rodata.cst4                                +0x0): first defined here
osbench: In function `_start':
(.text+0x0): multiple definition of `_start'
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_line): reloca                                tion 0 has invalid symbol index 2
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:/build/buildd                                /eglibc-2.15/csu/../sysdeps/x86_64/elf/start.S:109: first defined here
osbench: In function `_init':
(.init+0x0): multiple definition of `_init'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o:(.init+0x0):                                 first defined here
/tmp/ccOMIYX2.o:(.rodata+0x0): multiple definition of `numOfCallsPerTrial'
osbench:(.rodata+0x8): first defined here
/tmp/ccOMIYX2.o:(.rodata+0x8): multiple definition of `numOfTrials'
osbench:(.rodata+0x10): first defined here
/tmp/ccOMIYX2.o: In function `runLibCallTrial':
osbench.c:(.text+0x0): multiple definition of `runLibCallTrial'
osbench:(.text+0xe4): first defined here
/tmp/ccOMIYX2.o: In function `calcLibCallTime':
osbench.c:(.text+0xab): multiple definition of `calcLibCallTime'
osbench:(.text+0x18f): first defined here
/tmp/ccOMIYX2.o: In function `main':
osbench.c:(.text+0x143): multiple definition of `main'
osbench:(.text+0x38c): first defined here
/usr/lib/gcc/x86_64-linux-gnu/4.6/crtend.o:(.dtors+0x0): multiple definition of                                 `__DTOR_END__'
osbench:(.dtors+0x8): first defined here
/usr/bin/ld: error in osbench(.eh_frame); no .eh_frame_hdr table will be created                                .
collect2: ld returned 1 exit status

如有必要，我可以發布代碼，但是基准測試代碼部分用於作業分配，因此我不確定是否可以這樣做。 否則它可以很好地編譯，所以我不認為這是.c的問題謝謝。

Answer 1

-O不是-o 。 也就是說，大寫而不是小寫。 無論如何，您可以將其完全省略。 缺省值為-O0 。

如果不清楚， -o的含義不同。 它確定編譯輸出名稱。 因此，您應該將其保留在命令行中。 添加-O更改優化級別（或將其保留為默認設置）。 因此，實際上，您的原始構建已禁用優化。