Refactored variable length array code to use alloca()

While VLAs are supported in C99 and C11, they do pose some portability issues so best to avoid their use.

alloca() allocates on the stack frame and is free'd on exit from the function so essentially equivalent.

Ticket: ENT-14208
Changelog: none
(cherry picked from commit 6e95201)

Author: craigcomstock

cf-serverd/server_tls.c

@@ -226,8 +226,8 @@ bool ServerTLSPeek(ConnectionInfo *conn_info)
 
     const int peek_size = CF_INBAND_OFFSET + sizeof("CAUTH");
 
-    char buf[peek_size];
-    ssize_t got = recv(ConnectionInfoSocket(conn_info), buf, sizeof(buf), MSG_PEEK);
+    char *buf = alloca(peek_size);
+    ssize_t got = recv(ConnectionInfoSocket(conn_info), buf, peek_size, MSG_PEEK);
     assert(got <= peek_size);
     if (got < 0)
     {

libpromises/evalfunction.c

@@ -7396,9 +7396,8 @@ static FnCallResult FnCallClassFilterCsv(EvalContext *ctx,
                 }
                 else
                 {
-                    size_t const key_len = PRINTSIZE(size_t);
-                    char key[key_len];
-                    xsnprintf(key, key_len, "%zu", i);
+                    char key[PRINTSIZE(size_t)];
+                    xsnprintf(key, PRINTSIZE(size_t), "%zu", i);
 
                     JsonObjectAppendString(class_container,
                                            key,

libpromises/ornaments.c

@@ -156,7 +156,7 @@ void PromiseBanner(EvalContext *ctx, const Promise *pp)
     }
 
     const size_t n = 2*CF_MAXFRAGMENT + 3;
-    char pretty_promise_name[n+1];
+    char *pretty_promise_name = alloca(n+1);
     pretty_promise_name[0] = '\0';
     StringAppendAbbreviatedPromise(pretty_promise_name, pp->promiser, n, CF_MAXFRAGMENT);
     Log(LOG_LEVEL_VERBOSE, "P:    Promiser/affected object: '%s'", pretty_promise_name);

libpromises/syslog_client.c

@@ -27,6 +27,8 @@
 
 #include <cf3.defs.h>
 
+
+#define RFC3164_LENGTH 1024
 /*
  * Set by cf-agent/cf-serverd from body agent/server control.
  */
@@ -112,8 +114,7 @@ void RemoteSysLog(int log_priority, const char *log_string)
         }
         else
         {
-            const size_t rfc3164_len = 1024;
-            char message[rfc3164_len];
+            char message[RFC3164_LENGTH];
             char timebuffer[26];
             pid_t pid = getpid();
 

tests/acceptance/mock_package_manager.c

@@ -8,7 +8,7 @@
 static char AVAILABLE_PACKAGES_FILE_NAME[PATH_MAX];
 static char INSTALLED_PACKAGES_FILE_NAME[PATH_MAX];
 
-static const int MAX_PACKAGE_ENTRY_LENGTH = 256;
+#define MAX_PACKAGE_ENTRY_LENGTH 256
 
 #define DEFAULT_ARCHITECTURE "x666"