Experiment link
Compilation principle experiment – the use of GCC/Clang tool chain on the ARM architecture
Experiment report
Level 1: Understanding different representations of programs
## Question 1-1:
If executed on the command line
gcc -DNEG -E sample.c -o sample.i
What is the difference between the generated sample.i and the previous one?
According to the definition of NEG, and the choice of M is defined as -4
## Questions 1-2
Please compare sample-32.s and sample.s, find out their differences, and search the Internet to give the reasons for these differences. like:
- pushq and pushl
- rsp and esp
The difference between sample-32.s and sample.s
diff sample-32.s sample.s
1,4c1,6 < .file "sample.c" < .text < .globl main < .type main, @function --- > .arch armv8-a > .file "sample.c" > .text > .align 2 > .global main > .type main, %function 6,18c8,17 < .LFB0: < .cfi_startproc < pushl ?p < .cfi_def_cfa_offset 8 < .cfi_offset 5, -8 < movl %esp, ?p < .cfi_def_cfa_register 5 < subl $16, %esp < movl $4, -4(?p) < cmpl $0, -4(?p) < je.L2 < addl $4, -4(?p) < jmp.L3 --- > sub sp, sp, #16 > mov w0, -4 > str w0, [sp, 12] > ldr w0, [sp, 12] > cmp w0, 0 > beq.L2 > ldr w0, [sp, 12] > add w0, w0, 4 > str w0, [sp, 12] > b.L3 20c19,21 < sall $2, -4(?p) --- > ldr w0, [sp, 12] > lsl w0, w0, 2 > str w0, [sp, 12] 22,31c23,28 < movl $0, ?x < leave < .cfi_restore 5 < .cfi_def_cfa 4, 4 <ret < .cfi_endproc < .LFE0: < .size main, .-main < .ident "GCC: (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609" < .section .note.GNU-stack,"",@progbits --- > mov w0, 0 > add sp, sp, 16 > ret > .size main, .-main > .ident "GCC: (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609" > .section .note.GNU-stack,"",@progbits
Question 1-3 You can replace gcc with clang, repeat the above steps, and compare the similarities and differences between the output results of clang and gcc.
gcc sample.c -o sample -v clang sample.c -o sample -v
diff gcc.txt clang.txt 1,5c1,2 < Using built-in specs. < COLLECT_GCC=gcc < COLLECT_LTO_WRAPPER=/usr/lib/gcc/aarch64-linux-gnu/5/lto-wrapper < Target: aarch64-linux-gnu < Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.12' --with-bugurl=file:///usr/share/doc /gcc-5/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=- 5 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libquadmath --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr /lib/jvm/java-1.5.0-gcj-5-arm64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj- 5-arm64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-5-arm64 --with-arch-directory=aarch64 --with-ecj-jar= /usr/share/java/eclipse-ecj.jar --enable-multiarch --enable-fix-cortex-a53-843419 --dis able-werror --enable-checking=release --build=aarch64-linux-gnu --host=aarch64-linux-gnu --target=aarch64-linux-gnu --- > clang version 10.0.1 > Target: aarch64-unknown-linux-gnu 7,14c4,14 < gcc version 5.4.0 20160609 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.12) < COLLECT_GCC_OPTIONS='-o' 'sample' '-v' '-mlittle-endian' '-mabi=lp64' < /usr/lib/gcc/aarch64-linux-gnu/5/cc1 -quiet -v -imultiarch aarch64-linux-gnu sample.c -quiet -dumpbase sample.c -mlittle-endian -mabi=lp64 -auxbase sample - version -fstack-protector-strong -Wformat -Wformat-security -o /tmp/cc1Kcmw6.s < GNU C11 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.12) version 5.4.0 20160609 (aarch64-linux-gnu) < compiled by GNU C version 5.4.0 20160609, GMP version 6.1.0, MPFR version 3.1.4, MPC version 1.0.3 < GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 < ignoring nonexistent directory "/usr/local/include/aarch64-linux-gnu" < ignoring nonexistent directory "/usr/lib/gcc/aarch64-linux-gnu/5/../../../../aarch64-linux-gnu/include" --- > InstalledDir: /opt/llvm10/llvm-install/bin > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/5 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/5.4.0 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/6 > Found candidate GCC installation: /usr/lib/gcc/aarch64-linux-gnu/6.0.0 > Selected GCC installation: /usr/lib/gcc/aarch64-linux-gnu/5.4.0 > Candidate multilib: .;@m64 > Selected multilib: .;@m64 > "/opt/llvm10/llvm-install/bin/clang-10" -cc1 -triple aarch64-unknown-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard -value-names -main-file-name sample.c -mrelocation-model static -mthread-model posix -mframe-pointer=non-leaf -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases - target-cpu generic -target-feature + neon -target-abi aapcs -fallow-half-arguments-and-returns -dwarf-column-info -fno-split-dwarf-inlining -debugger-tuning=gdb -v -resource- dir /opt/llvm10/llvm-install/lib/clang/10.0.1 -internal-isystem /usr/local/include -internal-isystem /opt/llvm10/llvm-install/lib/clang/10.0.1/include - internal-externc-isystem /usr/include/aarch64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdebug-compilation-dir /data/workspace/myshixun -ferror-limit 19 -fmessage-length 0 -fno-signed-char -fgnuc-version=4.2.1 -fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics -faddrsig -o /tmp/sample- ee930b.o -x c sample.c > clang -cc1 version 10.0.1 based upon LLVM 10.0.1 default target aarch64-unknown-linux-gnu > ignoring nonexistent directory "/include" 17d16 < /usr/lib/gcc/aarch64-linux-gnu/5/include 19c18 < /usr/lib/gcc/aarch64-linux-gnu/5/include-fixed --- > /opt/llvm10/llvm-install/lib/clang/10.0.1/include 23,33c22 < GNU C11 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.12) version 5.4.0 20160609 (aarch64-linux-gnu) < compiled by GNU C version 5.4.0 20160609, GMP version 6.1.0, MPFR version 3.1.4, MPC version 1.0.3 < GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 < Compiler executable checksum: 0aba823f581e395c09d29a3a6f3b731f < COLLECT_GCC_OPTIONS='-o' 'sample' '-v' '-mlittle-endian' '-mabi=lp64' < as -v -EL -mabi=lp64 -o /tmp/cc281Jv1.o /tmp/cc1Kcmw6.s < GNU assembler version 2.26.1 (aarch64-linux-gnu) using BFD version (GNU Binutils for Ubuntu) 2.26.1 < COMPILER_PATH=/usr/lib/gcc/aarch64-linux-gnu/5/:/usr/lib/gcc/aarch64-linux-gnu/5/:/usr/lib/gcc/aarch64-linux-gnu/:/ usr/lib/gcc/aarch64-linux-gnu/5/:/usr/lib/gcc/aarch64-linux-gnu/ < LIBRARY_PATH=/usr/lib/gcc/aarch64-linux-gnu/5/:/usr/lib/gcc/aarch64-linux-gnu/5/../../../aarch64-linux-gnu/: /usr/lib/gcc/aarch64-linux-gnu/5/../../../../lib/:/lib/aarch64-linux-gnu/:/lib/../lib/:/ usr/lib/aarch64-linux-gnu/:/usr/lib/../lib/:/opt/llvm10/antlr4-cpp/dist/:/opt/llvm10/antlr4-cpp/dist/:./:/ usr/lib/gcc/aarch64-linux-gnu/5/../../../:/lib/:/usr/lib/ < COLLECT_GCC_OPTIONS='-o' 'sample' '-v' '-mlittle-endian' '-mabi=lp64' < /usr/lib/gcc/aarch64-linux-gnu/5/collect2 -plugin /usr/lib/gcc/aarch64-linux-gnu/5/liblto_plugin.so -plugin-opt=/usr/lib/gcc/aarch64 -linux-gnu/5/lto-wrapper -plugin-opt=-fresolution=/tmp/ccjhDePW.res -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s -plugin -opt=-pass-through=-lc -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s --sysroot=/ --build-id --eh-frame- hdr --hash-style=gnu --as-needed-dynamic-linker /lib/ld-linux-aarch64.so.1 -X -EL -maarch64linux --fix-cortex-a53-843419 -z relro -o sample /usr/lib/gcc/aarch64-linux-gnu/5/../../../aarch64-linux-gnu/crt1.o /usr/lib/gcc/aarch64-linux-gnu/5/.. /../../aarch64-linux-gnu/crti.o /usr/lib/gcc/aarch64-linux-gnu/5/crtbegin.o -L/usr/lib/gcc/aarch64-linux-gnu/5 -L/usr/lib/gcc/aarch64-linux-gnu/5/../../../aarch64-linux-gnu -L/usr/lib/gcc/aarch64-linux-gnu/5/.. /../../../lib -L/lib/aarch64-linux-gnu -L/lib/../lib -L/usr/lib/aarch64-linux-gnu -L/usr/lib/. ./lib -L/opt/llvm10/antlr4-cpp/dist -L/opt/llvm10/antl r4-cpp/dist -L. -L/usr/lib/gcc/aarch64-linux-gnu/5/../../../tmp/cc281Jv1.o -lgcc --as-needed -lgcc_s -- no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/aarch64-linux-gnu/5/crtend.o /usr/lib/gcc/aarch64- linux-gnu/5/../../../aarch64-linux-gnu/crtn.o --- > "/usr/bin/ld" -EL -z relro --hash-style=gnu --eh-frame-hdr -m aarch64linux -dynamic-linker /lib/ld-linux-aarch64.so.1 - o sample /usr/lib/gcc/aarch64-linux-gnu/5.4.0/../../../aarch64-linux-gnu/crt1.o /usr/lib/gcc/aarch64-linux-gnu/ 5.4.0/../../../aarch64-linux-gnu/crti.o /usr/lib/gcc/aarch64-linux-gnu/5.4.0/crtbegin.o -L/usr/lib/gcc /aarch64-linux-gnu/5.4.0-L/usr/lib/gcc/aarch64-linux-gnu/5.4.0/../../../aarch64-linux-gnu-L/lib/aarch64- linux-gnu -L/usr/lib/aarch64-linux-gnu -L/usr/lib/gcc/aarch64-linux-gnu/5.4.0/../../.. -L/opt/llvm10/llvm -install/bin/../lib -L/lib -L/usr/lib -L/opt/llvm10/antlr4-cpp/dist -L/opt/llvm10/antlr4-cpp/dist -L./tmp/sample -ee930b.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/aarch64-linux-gnu /5.4.0/crtend.o /usr/lib/gcc/aarch64-linux-gnu/5.4.0/../../../aarch64-linux-gnu/crtn.o
Level 2: Understand the compilation and linking of C programs that use libraries
Question 2-1:
What is the use of -nostdinc option?
Please list the default header file search path of the gcc C program on the EduCoder platform
How to make the above command compile while using the -nostdinc option? Please further explain the reason for passing (the source file cannot be modified).
Command option -nostdinc Do not search default path headers
-nostdinc: don’t look for files in standard system directories, just search directories specified by ‘-I’ option
root@evassh-17600448:/data/workspace/myshixun/lab2# gcc -E sample-io.c -o sample-io.i root@evassh-17600448:/data/workspace/myshixun/lab2# gcc sample-io.i -o sample-io root@evassh-17600448:/data/workspace/myshixun/lab2# ./sample-io Hello, world! a=8
Level 3: Compilation and compilation of C programs and comparison of various program representations
Write a sorting program in the file HW/H3/c/sort.c
#include<stdio.h>
#define N 1001
void selectSort(int a[], int n);
int main(){
int n;
scanf("%d", &n);
int a[N];
for(int i=0;i<n;i ++ ){
scanf("%d", &a[i]);
}
selectSort(a, n);
for(int i=0;i<n;i ++ ){
printf("%d ", a[i]);
}
printf("\\
");
return 0;
}
// sort function
void selectSort(int a[], int n)
{
for(int i=0;i<n;i ++ ){
int k=i;
for(int j=i + 1;j<n;j + + ){
if(a[j]<a[k]){
k=j;
}
}
if(k!=i){
int t=a[k];
a[k]=a[i];
a[i]=t;
}
}
}
Write compilation rules in the file HW/H3/c/Makefile
exe=sort
$(exe):$(wildcard *.c)
gcc -o $@ $^
.PHONY:clean
clean:
rm -f $(exe)
echo "clean object files"