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library: introduced 'Item_table' validation provisions

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The recent work on updating the <meminfo> and <vmstat>
modules with some newly added linux fields reminded me
(again) of a need for some mechanism guaranteeing that
a header file agrees with the source file assumptions.

Sadly, in the past, if a table entry was omitted or if
the table and header are ordered differently, then the
library would silently return the wrong results values
or even potentially experience a SIGSEGV abnormal end.

This patch offers a much needed development assist for
ensuring that Item_table entries are synchronized with
header file enumerators in terms of number plus order.

It's intended solely for our use as libprocps evolves.

Now, by activating ITEMTABLE_DEBUG, either directly or
via ./configure CFLAGS='-DITEMTABLE_DEBUG', the number
and order will be verified. It is envisioned that this
feature will be used at least once prior to a release.

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner
2020-08-10 00:00:00 -05:00
committed by Craig Small
parent c865b06c30
commit 92d0297e1e
6 changed files with 199 additions and 23 deletions
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36
proc/vmstat.c
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@ -41,6 +41,14 @@
#define VMSTAT_FILE "/proc/vmstat"
#define VMSTAT_BUFF 8192
/* ------------------------------------------------------------- +
this provision can be used to help ensure that our Item_table |
was synchronized with the enumerators found in the associated |
header file. It's intended to be used locally (& temporarily) |
at least once at some point prior to publishing new releases! | */
// #define ITEMTABLE_DEBUG //----------------------------------- |
// ------------------------------------------------------------- +
/*
* Perhaps someday we'll all learn what is in these fields. But |
* that might require available linux documentation progressing |
@ -557,7 +565,11 @@ HST_set(DELTA_ZONE_RECLAIM_FAILED, zone_reclaim_failed)
// ___ Controlling Table ||||||||||||||||||||||||||||||||||||||||||||||||||||||
typedef void (*SET_t)(struct vmstat_result *, struct vmstat_hist *);
#ifdef ITEMTABLE_DEBUG
#define RS(e) (SET_t)setNAME(e), VMSTAT_ ## e, STRINGIFY(VMSTAT_ ## e)
#else
#define RS(e) (SET_t)setNAME(e)
#endif
#define TS(t) STRINGIFY(t)
#define TS_noop ""
@ -568,6 +580,10 @@ typedef void (*SET_t)(struct vmstat_result *, struct vmstat_hist *);
* those 'enum vmstat_item' guys ! */
static struct {
SET_t setsfunc; // the actual result setting routine
#ifdef ITEMTABLE_DEBUG
int enumnumb; // enumerator (must match position!)
char *enum2str; // enumerator name as a char* string
#endif
char *type2str; // the result type as a string value
} Item_table[] = {
/* setsfunc type2str
@ -878,9 +894,6 @@ static struct {
{ RS(DELTA_WORKINGSET_REFAULT), TS(sl_int) },
{ RS(DELTA_WORKINGSET_RESTORE), TS(sl_int) },
{ RS(DELTA_ZONE_RECLAIM_FAILED), TS(sl_int) },
// dummy entry corresponding to VMSTAT_logical_end ...
{ NULL, NULL }
};
/* please note,
@ -1283,6 +1296,23 @@ PROCPS_EXPORT int procps_vmstat_new (
{
struct vmstat_info *p;
#ifdef ITEMTABLE_DEBUG
int i, failed = 0;
for (i = 0; i < MAXTABLE(Item_table); i++) {
if (i != Item_table[i].enumnumb) {
fprintf(stderr, "%s: enum/table error: Item_table[%d] was %s, but its value is %d\n"
, __FILE__, i, Item_table[i].enum2str, Item_table[i].enumnumb);
failed = 1;
}
}
if (i != VMSTAT_logical_end) {
fprintf(stderr, "%s: VMSTAT_logical_end is %d, expected %d\n"
, __FILE__, VMSTAT_logical_end, i);
failed = 1;
}
if (failed) _Exit(EXIT_FAILURE);
#endif
if (info == NULL || *info != NULL)
return -EINVAL;
if (!(p = calloc(1, sizeof(struct vmstat_info))))