gcc - 是否有与 gcc 的 __attribute__((section("name"))) 等效的 gfortran？
问题描述
我正在使用 nestedvm 包，其中包括一个修补的 Gnu gcc 编译器。对于这个包，可调用的用户方法/函数必须用 注释__attribute__((section(".text")))，如下面的 C 示例所示。
void echo(const char *string, int count) __attribute__((section(".text")));
void echo(const char *string, int count) {
int i;
for(i=0;i<count;i++)
printf("%d: %s\n",i,string);
}
我不知道修补编译器的内部工作原理，但是如果没有此注释，外部调用者将看不到用户函数。
如果使用 gfortran，如何为 Fortran 子例程和函数完成此注释？这可以用链接器脚本文件来完成吗？我可以为 Fortran 函数编写一个 C 包装器，但如果可能的话，我想避免这种情况。
** 更新 1 ** 使用 nm 来调查 .o 文件对这个问题有所了解......没有属性的 C 方法看起来像 sinkram 函数（在 nestedvm 中不可调用），而 echo 函数具有属性并且可以在nestedvm中调用：
Name Value Class Type Size Line Section
suckram |00000000| T | FUNC|00000078| |.text.suckram
echo |00000200| T | FUNC|00000074| |.text
我的 Fortran 对象中的 test1 子例程看起来像没有属性的吸盘方法：
test1_ |00000000| T | FUNC|00000080| |.text.test1_
根据我发现的一些nestedvm 文档，为了在nestedvm 中调用用户函数，它必须在该.text部分结束。
** 更新 2 ** 链接命令行如下。发表评论太长了。我删除了许多 .o 文件中的一些 (...)
mips-unknown-elf-gfortran -O3 -mmemcpy -ffunction-sections -fdata-sections -falign-functions=512 -fno-rename-registers -fno-schedule-insns -fno-delayed-branch -march=mips1 -specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec -I. -Wall -Wno-unused -o build/refprop/Refprop.mips build/refprop/NVM.o (...) build/refprop/TRNS_VIS.o build/refprop/MAIN.o -march=mips1 -specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec --static -Wl,--gc-sections -Wl,-Map=output1.map -Wl,--cref -lc -Wl,-Map=output.map -Wl,--cref
此外，即使我将代码作为库调用，nestedvm 也要求库具有用于初始化的 MAIN 例程。如果我在 MAIN 例程中对库函数进行一些虚拟调用，则在 MAIN 中调用的那些函数将移动到该.text部分，并变为可调用。
** 更新 3 ** make 的详细输出。我删除了许多 .o 文件中的一些 (...)
mips-unknown-elf-gfortran -O3 -mmemcpy -ffunction-sections -fdata-sections -falign-functions=512 -fno-rename-registers -fno-schedule-insns -fno-delayed-branch -march=mips1 -specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec -I. -Wall -Wno-unused -o build/refprop/Refprop.mips build/refprop/NVM.o (…) build/refprop/TRNS_VIS.o build/refprop/MAIN.o -march=mips1 -specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec --static -Wl,--gc-sections -Wl,-Map=output1.map -Wl,--cref -lc -Wl,-Map=output.map -Wl,--cref -v
Driving: mips-unknown-elf-gfortran -O3 -mmemcpy -ffunction-sections -fdata-sections -falign-functions=512 -fno-rename-registers -fno-schedule-insns -fno-delayed-branch -march=mips1 -specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec -I. -Wall -Wno-unused -o build/refprop/Refprop.mips build/refprop/NVM.o (…) build/refprop/TRNS_VIS.o build/refprop/MAIN.o -march=mips1 -specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec --static -Wl,--gc-sections -Wl,-Map=output1.map -Wl,--cref -lc -Wl,-Map=output.map -Wl,--cref -v -l gfortran -l m
Using built-in specs.
Reading specs from /home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec
Reading specs from /home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec
COLLECT_GCC=mips-unknown-elf-gfortran
COLLECT_LTO_WRAPPER=/home/jhuber/Documents/source/nestedvm/upstream/install/libexec/gcc/mips-unknown-elf/4.8.5/lto-wrapper
Target: mips-unknown-elf
Configured with: ../gcc-4.8.5/configure --prefix=/home/jhuber/Documents/source/nestedvm/upstream/install --target=mips-unknown-elf --disable-threads --disable-libssp --with-gnu-ld --with-gnu-as --with-newlib=yes --enable-sjlj-exceptions --enable-languages=c : (reconfigured) ../gcc-4.8.5/configure --prefix=/home/jhuber/Documents/source/nestedvm/upstream/install --target=mips-unknown-elf --disable-threads --disable-libssp --with-gnu-ld --with-gnu-as --with-newlib=yes --enable-sjlj-exceptions --enable-languages=c --enable-languages=c,c++,fortran
Thread model: single
gcc version 4.8.5 (GCC)
Reading specs from /home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/../../../../mips-unknown-elf/lib/libgfortran.spec
rename spec lib to liborig
COLLECT_GCC_OPTIONS='-O3' '-mmemcpy' '-ffunction-sections' '-fdata-sections' '-falign-functions=512' '-fno-rename-registers' '-fno-schedule-insns' '-fno-delayed-branch' '-march=mips1' '-specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec' '-I' '.' '-Wall' '-Wno-unused' '-o' 'build/refprop/Refprop.mips' '-march=mips1' '-specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec' '-static' '-v'
COMPILER_PATH=/home/jhuber/Documents/source/nestedvm/upstream/install/libexec/gcc/mips-unknown-elf/4.8.5/:/home/jhuber/Documents/source/nestedvm/upstream/install/libexec/gcc/mips-unknown-elf/4.8.5/:/home/jhuber/Documents/source/nestedvm/upstream/install/libexec/gcc/mips-unknown-elf/:/home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/:/home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/:/home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/../../../../mips-unknown-elf/bin/
LIBRARY_PATH=/home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/:/home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/../../../../mips-unknown-elf/lib/
COLLECT_GCC_OPTIONS='-O3' '-mmemcpy' '-ffunction-sections' '-fdata-sections' '-falign-functions=512' '-fno-rename-registers' '-fno-schedule-insns' '-fno-delayed-branch' '-march=mips1' '-specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec' '-I' '.' '-Wall' '-Wno-unused' '-o' 'build/refprop/Refprop.mips' '-march=mips1' '-specs=/home/jhuber/Documents/source/nestedvm/upstream/install/mips-unknown-elf/lib/crt0-override.spec' '-static' '-v'
/home/jhuber/Documents/source/nestedvm/upstream/install/libexec/gcc/mips-unknown-elf/4.8.5/collect2 -EB -o build/refprop/Refprop.mips /home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/crti.o /home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/crtbegin.o /home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/../../../../mips-unknown-elf/lib/crt0.o -L/home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5 -L/home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/../../../../mips-unknown-elf/lib build/refprop/NVM.o (…) build/refprop/TRNS_VIS.o build/refprop/MAIN.o --gc-sections -Map=output1.map --cref -lc -Map=output.map --cref -lgfortran -lm -lgcc -lm -lgcc -lgcc /home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/crtend.o /home/jhuber/Documents/source/nestedvm/upstream/install/lib/gcc/mips-unknown-elf/4.8.5/crtn.o
解决方案
我做了一些本地测试，并按-ffunction-sections预期将每个 fortran 函数放在自己的部分。相比：
$ gfortran -c -O3 -o hello.o hello.f90
$ objdump -h hello.o
hello.o: file format elf64-x86-64
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 000000aa 0000000000000000 0000000000000000 00000040 2**4
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
1 .data 00000000 0000000000000000 0000000000000000 000000ea 2**0
CONTENTS, ALLOC, LOAD, DATA
2 .bss 00000000 0000000000000000 0000000000000000 000000ea 2**0
ALLOC
3 .rodata.str1.1 0000000a 0000000000000000 0000000000000000 000000ea 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .text.startup 00000026 0000000000000000 0000000000000000 00000100 2**4
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
5 .rodata 0000001c 0000000000000000 0000000000000000 00000130 2**4
CONTENTS, ALLOC, LOAD, READONLY, DATA
6 .comment 00000026 0000000000000000 0000000000000000 0000014c 2**0
CONTENTS, READONLY
7 .note.GNU-stack 00000000 0000000000000000 0000000000000000 00000172 2**0
CONTENTS, READONLY
8 .eh_frame 00000068 0000000000000000 0000000000000000 00000178 2**3
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
至：
$ gfortran -ffunction-sections -c -O3 -o hello.o hello.f90
$ objdump -h hello.o
hello.o: file format elf64-x86-64
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 00000000 0000000000000000 0000000000000000 00000040 2**0
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .data 00000000 0000000000000000 0000000000000000 00000040 2**0
CONTENTS, ALLOC, LOAD, DATA
2 .bss 00000000 0000000000000000 0000000000000000 00000040 2**0
ALLOC
3 .rodata.str1.1 0000000a 0000000000000000 0000000000000000 00000040 2**0
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .text.MAIN__ 00000097 0000000000000000 0000000000000000 00000050 2**4
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
5 .text.foo_ 0000000a 0000000000000000 0000000000000000 000000f0 2**4
CONTENTS, ALLOC, LOAD, READONLY, CODE
6 .text.startup.main 00000026 0000000000000000 0000000000000000 00000100 2**4
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
7 .rodata 0000001c 0000000000000000 0000000000000000 00000130 2**4
CONTENTS, ALLOC, LOAD, READONLY, DATA
8 .comment 00000026 0000000000000000 0000000000000000 0000014c 2**0
CONTENTS, READONLY
9 .note.GNU-stack 00000000 0000000000000000 0000000000000000 00000172 2**0
CONTENTS, READONLY
10 .eh_frame 00000068 0000000000000000 0000000000000000 00000178 2**3
CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
默认情况下，我本地机器上的内置链接器脚本会将所有这些都卷入其中.text。看起来你链接的任何东西都没有。您应该能够修改该脚本以执行您正在尝试的操作。这比属性扩展要困难一些，因为您必须在单独的文件中维护列表，但您应该能够找到您喜欢的任何内容。如果您在问题中提供更多有关此内容的背景信息，我可以在这里举一个例子。
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