英文:
Why aren't const variables visible in obj file after compilation in C++ using Visual Studio?
问题
我有一个VisualStudio的C++项目，里面有一个名为Test.c的文件，标记为'Compile as C++ Code (/TP)'。
Test.c文件中只包含以下变量：
const int test123 = 100;
编译后，我在Test.obj文件中找不到这个变量。我使用了'dumpbin /symbols'命令导出了obj文件。这个变量不在obj文件中可能的原因是什么？
- obj文件只包含以下项目：
File Type: COFF OBJECTCOFF SYMBOL TABLE000 010575C2 ABS notype Static | @comp.id001 80010390 ABS notype Static | @feat.00002 00000002 ABS notype Static | @vol.md003 00000000 SECT1 notype Static | .drectveSection length 41, #relocs 0, #linenums 0, checksum 0Relocation CRC 00000000006 00000000 SECT2 notype Static | .debug$SSection length F8, #relocs 0, #linenums 0, checksum 0Relocation CRC 00000000009 00000000 SECT3 notype Static | .debug$TSection length 78, #relocs 0, #linenums 0, checksum 0Relocation CRC 0000000000C 00000000 SECT4 notype Static | .chks64Section length 20, #relocs 0, #linenums 0, checksum 0Relocation CRC 00000000String Table Size = 0x0 bytesSummary20 .chks64F8 .debug$S78 .debug$T41 .drectve
删除'const'后，变量在obj文件中可用。
英文:
I have a VisualStudio C++ project with a Test.c file and it is marked as 'Compile as C++ Code (/TP)'.
The Test.c contains only the below variable,
const int test123 = 100;
After compilation, I could not find this variable in Test.obj file. I have used 'dumpbin /symbols' command to export the obj file. What could be the reason for this variable not available in obj file?
- objfile contains only below items
File Type: COFF OBJECTCOFF SYMBOL TABLE000 010575C2 ABS notype Static | @comp.id001 80010390 ABS notype Static | @feat.00002 00000002 ABS notype Static | @vol.md003 00000000 SECT1 notype Static | .drectveSection length 41, #relocs 0, #linenums 0, checksum 0Relocation CRC 00000000006 00000000 SECT2 notype Static | .debug$SSection length F8, #relocs 0, #linenums 0, checksum 0Relocation CRC 00000000009 00000000 SECT3 notype Static | .debug$TSection length 78, #relocs 0, #linenums 0, checksum 0Relocation CRC 0000000000C 00000000 SECT4 notype Static | .chks64Section length 20, #relocs 0, #linenums 0, checksum 0Relocation CRC 00000000String Table Size = 0x0 bytesSummary20 .chks64F8 .debug$S78 .debug$T41 .drectve
The variable is available in obj after removing the 'const'.
答案1
得分: 4
全局的C++ const变量具有静态链接，这就解释了为什么在目标文件中看不到它作为一个符号。
链接：https://learn.microsoft.com/en-us/cpp/error-messages/tool-errors/global-constants-in-cpp?view=msvc-170
此外，这在这个回答中也有很好的解释（https://stackoverflow.com/questions/998425/why-does-const-imply-internal-linkage-in-c-when-it-doesnt-in-c）。
英文:
Global const variables in C++ have static linkage and that explains why you don't see it as a symbol in the object file.
Also, this is well explained in this answer.
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