link modifier `export-symbols`: export all global symbols from selected uptream c static libraries
In order to be able to export symbols from a specified upstream C static library, I redesigned a solution that, compared to a previous PR rust-lang/rust#150335 I submitted, will not have any extra symbols leaking out.
The following points should be noted:
- This attribute will select and import the `Global` symbols of the first matching library it finds.
- Developers should ensure that there are no libraries with the same name.
- This modifier is only compatible with `static` linking kind
- By default, upstream C static libraries will not export their `Global` symbols regardless of whether `LTO` optimization is enabled. However, after enabling this attribute, if the upstream C static library has `LTO` optimization enabled, the compiler will issue an error to inform the developer that the linked C library is invalid.
The test code is the same as the PR rust-lang/rust#150335.
Here are the results:
1. `cargo +include-libs rustc --release -- -L. -lstatic:+export-symbols=c_add`
(or you can use `#[link(name = "c_add", kind= "static", modifier = "+export-symbols")]` in the file)
```bash
U abort@GLIBC_2.2.5
U bcmp@GLIBC_2.2.5
0000000000014f60 T c_add
U calloc@GLIBC_2.2.5
U close@GLIBC_2.2.5
0000000000014f70 T c_sub
w __cxa_finalize@GLIBC_2.2.5
w __cxa_thread_atexit_impl@GLIBC_2.18
U dl_iterate_phdr@GLIBC_2.2.5
0000000000014ee0 T downstream_add
U __errno_location@GLIBC_2.2.5
U free@GLIBC_2.2.5
U fstat64@GLIBC_2.33
U getcwd@GLIBC_2.2.5
U getenv@GLIBC_2.2.5
w __gmon_start__
w _ITM_deregisterTMCloneTable
w _ITM_registerTMCloneTable
U lseek64@GLIBC_2.2.5
U malloc@GLIBC_2.2.5
U memcpy@GLIBC_2.14
U memmove@GLIBC_2.2.5
U memset@GLIBC_2.2.5
U mmap64@GLIBC_2.2.5
U munmap@GLIBC_2.2.5
U open64@GLIBC_2.2.5
U posix_memalign@GLIBC_2.2.5
U pthread_key_create@GLIBC_2.34
U pthread_key_delete@GLIBC_2.34
U pthread_setspecific@GLIBC_2.34
U read@GLIBC_2.2.5
U readlink@GLIBC_2.2.5
U realloc@GLIBC_2.2.5
U realpath@GLIBC_2.3
U stat64@GLIBC_2.33
w statx@GLIBC_2.28
U strlen@GLIBC_2.2.5
U syscall@GLIBC_2.2.5
U __tls_get_addr@GLIBC_2.3
U _Unwind_Backtrace@GCC_3.3
U _Unwind_DeleteException@GCC_3.0
U _Unwind_GetDataRelBase@GCC_3.0
U _Unwind_GetIP@GCC_3.0
U _Unwind_GetIPInfo@GCC_4.2.0
U _Unwind_GetLanguageSpecificData@GCC_3.0
U _Unwind_GetRegionStart@GCC_3.0
U _Unwind_GetTextRelBase@GCC_3.0
U _Unwind_RaiseException@GCC_3.0
U _Unwind_Resume@GCC_3.0
U _Unwind_SetGR@GCC_3.0
U _Unwind_SetIP@GCC_3.0
U write@GLIBC_2.2.5
U writev@GLIBC_2.2.5
```
3. `cargo +nightly rustc --release -- -L ./`
```bash
U abort@GLIBC_2.2.5
U bcmp@GLIBC_2.2.5
U calloc@GLIBC_2.2.5
U close@GLIBC_2.2.5
w __cxa_finalize@GLIBC_2.2.5
w __cxa_thread_atexit_impl@GLIBC_2.18
U dl_iterate_phdr@GLIBC_2.2.5
0000000000011e10 T downstream_add
U __errno_location@GLIBC_2.2.5
U free@GLIBC_2.2.5
U fstat64@GLIBC_2.33
U getcwd@GLIBC_2.2.5
U getenv@GLIBC_2.2.5
w gettid@GLIBC_2.30
w __gmon_start__
w _ITM_deregisterTMCloneTable
w _ITM_registerTMCloneTable
U lseek64@GLIBC_2.2.5
U malloc@GLIBC_2.2.5
U memcpy@GLIBC_2.14
U memmove@GLIBC_2.2.5
U memset@GLIBC_2.2.5
U mmap64@GLIBC_2.2.5
U munmap@GLIBC_2.2.5
U open64@GLIBC_2.2.5
U posix_memalign@GLIBC_2.2.5
U pthread_key_create@GLIBC_2.34
U pthread_key_delete@GLIBC_2.34
U pthread_setspecific@GLIBC_2.34
U read@GLIBC_2.2.5
U readlink@GLIBC_2.2.5
U realloc@GLIBC_2.2.5
U realpath@GLIBC_2.3
U stat64@GLIBC_2.33
w statx@GLIBC_2.28
U strlen@GLIBC_2.2.5
U syscall@GLIBC_2.2.5
U __tls_get_addr@GLIBC_2.3
U _Unwind_Backtrace@GCC_3.3
U _Unwind_GetDataRelBase@GCC_3.0
U _Unwind_GetIP@GCC_3.0
U _Unwind_GetIPInfo@GCC_4.2.0
U _Unwind_GetLanguageSpecificData@GCC_3.0
U _Unwind_GetRegionStart@GCC_3.0
U _Unwind_GetTextRelBase@GCC_3.0
U _Unwind_RaiseException@GCC_3.0
U _Unwind_Resume@GCC_3.0
U _Unwind_SetGR@GCC_3.0
U _Unwind_SetIP@GCC_3.0
U write@GLIBC_2.2.5
U writev@GLIBC_2.2.5
```
r? @bjorn3
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