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add code/C/packtest.c

This commit is contained in:
tTh 2024-03-27 11:05:42 +01:00
parent 0818f87582
commit 66bc3d19c4
3 changed files with 122 additions and 1 deletions
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1
code/C/.gitignore vendored
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@ -1,2 +1,3 @@
fgets-simple
demo-strtok
packtest

6
code/C/Makefile
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@ -2,7 +2,7 @@
# exemples pour le chapitre sur le C
# new Sat Feb 11 12:06:34 CET 2023
all: no-op slowprint fgets-simple
all: no-op slowprint fgets-simple packtest
no-op: no-op.c Makefile
gcc -Wall $< -o $@
@ -15,3 +15,7 @@ fgets-simple: fgets-simple.c Makefile
demo-strtok: demo-strtok.c Makefile
gcc -Wall $< -o $@
# added Wed Mar 27 10:01:41 UTC 2024
packtest: packtest.c
gcc -Wall $< -o $@

116
code/C/packtest.c Executable file
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@ -0,0 +1,116 @@
#include <stdio.h>
#include <stdbool.h>
/*
* found in the good old Usenet
*/
/* The expected sizes in these comments assime a 64-bit machine */
struct foo1 {
char *p;
char c;
long x;
};
struct foo2 {
char c; /* 1 byte */
char pad[7]; /* 7 bytes */
char *p; /* 8 bytes */
long x; /* 8 bytes */
};
struct foo3 {
char *p; /* 8 bytes */
char c; /* 1 byte */
};
struct foo4 {
short s; /* 2 bytes */
char c; /* 1 byte */
};
struct foo5 {
char c;
struct foo5_inner {
char *p;
short x;
} inner;
};
struct foo6 {
short s;
char c;
int flip:1;
int nybble:4;
int septet:7;
};
struct foo7 {
int bigfield:31;
int littlefield:1;
};
struct foo8 {
int bigfield1:31;
int littlefield1:1;
int bigfield2:31;
int littlefield2:1;
};
struct foo9 {
int bigfield1:31;
int bigfield2:31;
int littlefield1:1;
int littlefield2:1;
};
struct foo10 {
char c;
struct foo10 *p;
short x;
};
struct foo11 {
struct foo11 *p;
short x;
char c;
};
struct foo12 {
struct foo12_inner {
char *p;
short x;
} inner;
char c;
};
int main(int argc, char *argv[])
{
printf("sizeof(char *) = %zu\n", sizeof(char *));
printf("sizeof(long) = %zu\n", sizeof(long));
printf("sizeof(int) = %zu\n", sizeof(int));
printf("sizeof(short) = %zu\n", sizeof(short));
printf("sizeof(char) = %zu\n", sizeof(char));
printf("sizeof(float) = %zu\n", sizeof(float));
printf("sizeof(double) = %zu\n", sizeof(double));
printf("sizeof(struct foo1) = %zu\n", sizeof(struct foo1));
printf("sizeof(struct foo2) = %zu\n", sizeof(struct foo2));
printf("sizeof(struct foo3) = %zu\n", sizeof(struct foo3));
printf("sizeof(struct foo4) = %zu\n", sizeof(struct foo4));
printf("sizeof(struct foo5) = %zu\n", sizeof(struct foo5));
printf("sizeof(struct foo6) = %zu\n", sizeof(struct foo6));
printf("sizeof(struct foo7) = %zu\n", sizeof(struct foo7));
printf("sizeof(struct foo8) = %zu\n", sizeof(struct foo8));
printf("sizeof(struct foo9) = %zu\n", sizeof(struct foo9));
printf("sizeof(struct foo10) = %zu\n", sizeof(struct foo10));
printf("sizeof(struct foo11) = %zu\n", sizeof(struct foo11));
printf("sizeof(struct foo12) = %zu\n", sizeof(struct foo12));
if (sizeof(struct foo3) == 16) {
puts("This looks like a 64-bit machine.");
} else if (sizeof(struct foo3) == 6) {
puts("This looks like a 32-bit machine.");
}
}