I am using the nestedvm package, which includes a patched Gnu gcc compiler. For this package, callable user methods/functions have to annotated with __attribute__((section(".text"))), as shown in the C example below.
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);
}
I don't know about the inner workings of the patched compiler, but without this annotation, the user function is not visible to outside callers.
If using gfortran, how can I accomplish this annotation for Fortran subroutines and functions? Could this be done with a linker script file? I could write a C wrapper to the Fortran functions, but would like to avoid this if possible.
** UPDATE 1 ** Using nm to investigate the .o file sheds some light on the issue...a C method without the attribute looks like the suckram function (which is not callable in nestedvm), while the echo function has the attribute and is callable in nestedvm:
Name Value Class Type Size Line Section
suckram |00000000| T | FUNC|00000078| |.text.suckram
echo |00000200| T | FUNC|00000074| |.text
The test1 subroutine in my Fortran object looks like the suckram method without the attribute:
test1_ |00000000| T | FUNC|00000080| |.text.test1_
According to some nestedvm documentation I found, in order for a user function to be callable in nestedvm, it has to end up in the .text section.
** UPDATE 2 ** A link command line is below. It is too long to put in a comment. I removed some of the many .o files (…)
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
Also, even though I am calling the code as a library, nestedvm requires the library to have a MAIN routine for initialization. If I make some dummy calls to the library functions in the MAIN routine, those functions that are called in MAIN are moved the .text section, and become callable.
** UPDATE 3 ** Verbose output from make. I removed some of the many .o files (…)
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