Explicitly check sscanf(3) and fscanf(3) return values

Compare the return value of sscanf(3) and fscanf(3) explicitly against
the expected number of parsed items and avoid implicit boolean
conversion.  Such an implicit conversion would treat EOF (-1) the same
as at least one item parsed successfully.

Reported by CodeQL.

Header.c

@@ -86,10 +86,9 @@ static void Header_addMeterByName(Header* this, const char* name, MeterModeId mo
    unsigned int param = 0;
    size_t nameLen;
    if (paren) {
-      int ok = sscanf(paren, "(%10u)", &param); // CPUMeter
-      if (!ok) {
+      if (sscanf(paren, "(%10u)", &param) != 1) { // not CPUMeter
          char dynamic[32] = {0};
-         if (sscanf(paren, "(%30s)", dynamic)) { // DynamicMeter
+         if (sscanf(paren, "(%30s)", dynamic) == 1) { // DynamicMeter
             char* end;
             if ((end = strrchr(dynamic, ')')) == NULL)
                return;    // htoprc parse failure

Settings.c

@@ -240,7 +240,7 @@ static int toFieldIndex(Hashtable* columns, const char* str) {
    } else {
       // Dynamically-defined columns are always stored by-name.
       char dynamic[32] = {0};
-      if (sscanf(str, "Dynamic(%30s)", dynamic)) {
+      if (sscanf(str, "Dynamic(%30s)", dynamic) == 1) {
          char* end;
          if ((end = strrchr(dynamic, ')')) != NULL) {
             bool success;

linux/LinuxMachine.c

@@ -302,8 +302,8 @@ static void LinuxMachine_scanZramInfo(LinuxMachine* this) {
       memory_t orig_data_size = 0;
       memory_t compr_data_size = 0;
 
-      if (!fscanf(disksize_file, "%llu\n", &size) ||
-          !fscanf(mm_stat_file, "    %llu       %llu", &orig_data_size, &compr_data_size)) {
+      if (1 != fscanf(disksize_file, "%llu\n", &size) ||
+          2 != fscanf(mm_stat_file, "    %llu       %llu", &orig_data_size, &compr_data_size)) {
          fclose(disksize_file);
          fclose(mm_stat_file);
          break;
@@ -342,10 +342,10 @@ static void LinuxMachine_scanZfsArcstats(LinuxMachine* this) {
             sscanf(buffer + strlen(label), " %*2u %32llu", variable);          \
             break;                                                             \
          } else (void) 0 /* Require a ";" after the macro use. */
-      #define tryReadFlag(label, variable, flag)                               \
-         if (String_startsWith(buffer, label)) {                               \
-            (flag) = sscanf(buffer + strlen(label), " %*2u %32llu", variable); \
-            break;                                                             \
+      #define tryReadFlag(label, variable, flag)                                      \
+         if (String_startsWith(buffer, label)) {                                      \
+            (flag) = (1 == sscanf(buffer + strlen(label), " %*2u %32llu", variable)); \
+            break;                                                                    \
          } else (void) 0 /* Require a ";" after the macro use. */
 
       switch (buffer[0]) {

linux/LinuxProcessTable.c

@@ -426,29 +426,29 @@ static bool LinuxProcessTable_readStatusFile(Process* process, openat_arg_t proc
       } else if (String_startsWith(buffer, "voluntary_ctxt_switches:")) {
          unsigned long vctxt;
          int ok = sscanf(buffer, "voluntary_ctxt_switches:\t%lu", &vctxt);
-         if (ok >= 1) {
+         if (ok == 1) {
             ctxt += vctxt;
          }
 
       } else if (String_startsWith(buffer, "nonvoluntary_ctxt_switches:")) {
          unsigned long nvctxt;
          int ok = sscanf(buffer, "nonvoluntary_ctxt_switches:\t%lu", &nvctxt);
-         if (ok >= 1) {
+         if (ok == 1) {
             ctxt += nvctxt;
          }
 
 #ifdef HAVE_VSERVER
       } else if (String_startsWith(buffer, "VxID:")) {
          int vxid;
          int ok = sscanf(buffer, "VxID:\t%32d", &vxid);
-         if (ok >= 1) {
+         if (ok == 1) {
             lp->vxid = vxid;
          }
 #ifdef HAVE_ANCIENT_VSERVER
       } else if (String_startsWith(buffer, "s_context:")) {
          int vxid;
          int ok = sscanf(buffer, "s_context:\t%32d", &vxid);
-         if (ok >= 1) {
+         if (ok == 1) {
             lp->vxid = vxid;
          }
 #endif /* HAVE_ANCIENT_VSERVER */
@@ -938,7 +938,7 @@ static void LinuxProcessTable_readOomData(LinuxProcess* process, openat_arg_t pr
    if (fgets(buffer, PROC_LINE_LENGTH, file)) {
       unsigned int oom;
       int ok = sscanf(buffer, "%u", &oom);
-      if (ok >= 1) {
+      if (ok == 1) {
          process->oom = oom;
       }
    }

linux/Platform.c

@@ -261,7 +261,7 @@ int Platform_getUptime(void) {
    if (fd) {
       int n = fscanf(fd, "%64lf", &uptime);
       fclose(fd);
-      if (n <= 0) {
+      if (n != 1) {
          return 0;
       }
    }