add code/C/packtest.c

code/C/.gitignore

@@ -1,2 +1,3 @@
 fgets-simple
 demo-strtok
+packtest

code/C/Makefile

@@ -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 $@

code/C/packtest.c

@@ -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.");
+    }
+	 
+}