inifile: Migrate C callers to new reentrant iniFindString() API

Follow-up to the C++ IniFile::Find() reentrancy fix. The previous
commit changed Find() to return std::string by value, but the C API
wrapper iniFind() still used static storage, making it non-reentrant.

Add iniFindString() that takes a caller-provided buffer, making it
safe for concurrent use and multiple sequential calls. Reimplement
iniFind() as a deprecated wrapper around iniFindString().

Migrate all C callers to iniFindString():
- mb2hal: 11 call sites
- vfdb_vfd: 2 call sites
- vfs11_vfd: 4 call sites
- halcmd: 2 call sites

Also clean up dead commented-out code in mb2hal and halrmt.

Author: Luca Toniolo

src/hal/user_comps/mb2hal/mb2hal_init.c

@@ -79,6 +79,7 @@ retCode parse_common_section()
     char *fnct_name = "parse_common_section";
     char *section = "MB2HAL_INIT", *tag;
     const char *tmpstr;
+    char tmpbuf[INI_MAX_LINELEN];
 
     if (gbl.ini_file_ptr == NULL) {
         ERR(gbl.init_dbg, "gbl.ini_file_ptr NULL pointer");
@@ -90,7 +91,7 @@ retCode parse_common_section()
     DBG(gbl.init_dbg, "[%s] [%s] [%d]", section, tag, gbl.init_dbg);
 
     tag     = "VERSION"; //optional
-    tmpstr = iniFind(gbl.ini_file_ptr, tag, section);
+    tmpstr = iniFindString(gbl.ini_file_ptr, tag, section, tmpbuf, sizeof(tmpbuf));
     if (tmpstr != NULL) {
         int major, minor;
         sscanf(tmpstr, "%d.%d", &major, &minor);
@@ -99,7 +100,7 @@ retCode parse_common_section()
     DBG(gbl.init_dbg, "[%s] [%s] [%d]", section, tag, gbl.version);
 
     tag    = "HAL_MODULE_NAME"; //optional
-    tmpstr = iniFind(gbl.ini_file_ptr, tag, section);
+    tmpstr = iniFindString(gbl.ini_file_ptr, tag, section, tmpbuf, sizeof(tmpbuf));
     if (tmpstr != NULL) {
         gbl.hal_mod_name = strdup(tmpstr);
     }
@@ -176,6 +177,7 @@ retCode parse_transaction_section(const int mb_tx_num)
     char section[40];
     char *tag;
     const char *tmpstr;
+    char tmpbuf[INI_MAX_LINELEN];
     mb_tx_t *this_mb_tx;
 
     if (gbl.ini_file_ptr == NULL) {
@@ -197,7 +199,7 @@ retCode parse_transaction_section(const int mb_tx_num)
     snprintf(section, sizeof(section)-1, "TRANSACTION_%02d", mb_tx_num);
 
     tag = "LINK_TYPE"; //required 1st time, then optional
-    tmpstr = iniFind(gbl.ini_file_ptr, tag, section);
+    tmpstr = iniFindString(gbl.ini_file_ptr, tag, section, tmpbuf, sizeof(tmpbuf));
     if (tmpstr != NULL) {
         if (strcasecmp(tmpstr, "tcp") == retOK) {
             this_mb_tx->cfg_link_type = linkTCP;
@@ -274,7 +276,7 @@ retCode parse_transaction_section(const int mb_tx_num)
 
 
     tag = "PIN_NAMES";
-    tmpstr = iniFind(gbl.ini_file_ptr, tag, section);
+    tmpstr = iniFindString(gbl.ini_file_ptr, tag, section, tmpbuf, sizeof(tmpbuf));
     if (tmpstr != NULL) {
         if(parse_pin_names(tmpstr, this_mb_tx) != retOK)
         {
@@ -344,7 +346,7 @@ retCode parse_transaction_section(const int mb_tx_num)
     DBG(gbl.init_dbg, "[%s] [%s] [%d]", section, tag, this_mb_tx->cfg_debug);
 
     tag = "MB_TX_CODE"; //required
-    tmpstr = iniFind(gbl.ini_file_ptr, tag, section);
+    tmpstr = iniFindString(gbl.ini_file_ptr, tag, section, tmpbuf, sizeof(tmpbuf));
     if (tmpstr != NULL) {
         int i;
         for (i=0 ; i<mbtxMAX; i++) {
@@ -367,7 +369,7 @@ retCode parse_transaction_section(const int mb_tx_num)
     DBG(gbl.init_dbg, "[%s] [%s] [%s] [%d]", section, tag, this_mb_tx->mb_tx_fnct_name, this_mb_tx->mb_tx_fnct);
 
     tag = "HAL_TX_NAME"; //optional
-    tmpstr = iniFind(gbl.ini_file_ptr, tag, section);
+    tmpstr = iniFindString(gbl.ini_file_ptr, tag, section, tmpbuf, sizeof(tmpbuf));
     if (tmpstr != NULL) {
         strncpy(this_mb_tx->hal_tx_name, tmpstr, HAL_NAME_LEN);
     }
@@ -376,32 +378,6 @@ retCode parse_transaction_section(const int mb_tx_num)
     }
     DBG(gbl.init_dbg, "[%s] [%s] [%s]", section, tag, this_mb_tx->hal_tx_name);
 
-    /*
-        str = iniFind(gbl.ini_file_ptr, "PINNAME", mb_tx_name);
-        if (str != NULL) {
-            pin_name = malloc(strlen(str) + 1);
-            rtapi_strxcpy(pin_name, str);	// convert a const string into one
-            // we can modify
-        }
-        else {
-            pin_name = malloc(1);	// empty string
-            *pin_name = 0;
-        }
-        if (mb_tx->name[0] != 0) {
-            strncpy(mb_tx_name, mb_tx->name, HAL_NAME_LEN);
-        }
-        else {
-            snprintf(mb_tx_name, sizeof(mb_tx_name), "%02d", mb_tx_num);
-        }
-        memcpy(&gbl.mb_tx[mb_tx_num], mb_tx, sizeof(mb_tx_t));
-        rc = create_pins(mb_tx_name, &gbl.mb_tx[mb_tx_num], pin_name);
-        free(pin_name);
-        if (rc != retOK) {
-            ERR(gbl.init_dbg, "Failed to create pins");
-            return retERR;
-        }
-    */
-
     return retOK;
 }
 
@@ -410,6 +386,7 @@ retCode parse_tcp_subsection(const char *section, const int mb_tx_num)
     char *fnct_name="parse_tcp_subsection";
     char *tag;
     const char *tmpstr;
+    char tmpbuf[INI_MAX_LINELEN];
     mb_tx_t *this_mb_tx;
 
     if (gbl.ini_file_ptr == NULL || section == NULL) {
@@ -424,7 +401,7 @@ retCode parse_tcp_subsection(const char *section, const int mb_tx_num)
     this_mb_tx = &gbl.mb_tx[mb_tx_num];
 
     tag = "TCP_IP"; //required 1st time, then optional
-    tmpstr = iniFind(gbl.ini_file_ptr, tag, section);
+    tmpstr = iniFindString(gbl.ini_file_ptr, tag, section, tmpbuf, sizeof(tmpbuf));
     if (tmpstr != NULL) {
         strncpy(this_mb_tx->cfg_tcp_ip, tmpstr, sizeof(this_mb_tx->cfg_tcp_ip)-1);
     }
@@ -466,6 +443,7 @@ retCode parse_serial_subsection(const char *section, const int mb_tx_num)
     char *fnct_name="parse_serial_subsection";
     char *tag;
     const char *tmpstr;
+    char tmpbuf[INI_MAX_LINELEN];
     mb_tx_t *this_mb_tx;
 
     if (gbl.ini_file_ptr == NULL || section == NULL) {
@@ -480,7 +458,7 @@ retCode parse_serial_subsection(const char *section, const int mb_tx_num)
     this_mb_tx = &gbl.mb_tx[mb_tx_num];
 
     tag = "SERIAL_PORT"; //required 1st time
-    tmpstr = iniFind(gbl.ini_file_ptr, tag, section);
+    tmpstr = iniFindString(gbl.ini_file_ptr, tag, section, tmpbuf, sizeof(tmpbuf));
     if (tmpstr != NULL) {
         strncpy(this_mb_tx->cfg_serial_device, tmpstr, sizeof(this_mb_tx->cfg_serial_device)-1);
     }
@@ -548,7 +526,7 @@ retCode parse_serial_subsection(const char *section, const int mb_tx_num)
     DBG(gbl.init_dbg, "[%s] [%s] [%d]", section, tag, this_mb_tx->cfg_serial_data_bit);
 
     tag = "SERIAL_PARITY"; //required 1st time
-    tmpstr = iniFind(gbl.ini_file_ptr, tag, section);
+    tmpstr = iniFindString(gbl.ini_file_ptr, tag, section, tmpbuf, sizeof(tmpbuf));
     if (tmpstr != NULL) {
         strncpy(this_mb_tx->cfg_serial_parity, tmpstr, sizeof(this_mb_tx->cfg_serial_parity)-1);
     }

src/hal/user_comps/vfdb_vfd/vfdb_vfd.c

@@ -278,11 +278,12 @@ enum kwdresult {NAME_NOT_FOUND, KEYWORD_INVALID, KEYWORD_FOUND};
 int findkwd(param_pointer p, const char *name, int *result, const char *keyword, int value, ...)
 {
     const char *word;
+    char wordbuf[INI_MAX_LINELEN];
     va_list ap;
     const char *kwds[MAX_KWD], **s;
     int nargs = 0;
 
-    if ((word = iniFind(p->fp, name, p->section)) == NULL)
+    if ((word = iniFindString(p->fp, name, p->section, wordbuf, sizeof(wordbuf))) == NULL)
         return NAME_NOT_FOUND;
 
     kwds[nargs++] = keyword;
@@ -311,6 +312,7 @@ int findkwd(param_pointer p, const char *name, int *result, const char *keyword,
 int read_ini(param_pointer p)
 {
     const char *s;
+    char sbuf[INI_MAX_LINELEN];
     int value;
 
     if ((p->fp = fopen(p->inifile,"r")) != NULL) {
@@ -328,7 +330,7 @@ int read_ini(param_pointer p)
         iniFindInt(p->fp, "MOTOR_HZ", p->section, &p->motor_hz);
         iniFindInt(p->fp, "MOTOR_RPM", p->section, &p->motor_rpm);
 
-        if ((s = iniFind(p->fp, "DEVICE", p->section))) {
+        if ((s = iniFindString(p->fp, "DEVICE", p->section, sbuf, sizeof(sbuf)))) {
             p->device = strdup(s);
         }
         value = p->parity;

src/hal/user_comps/vfs11_vfd/vfs11_vfd.c

@@ -398,11 +398,12 @@ enum kwdresult {NAME_NOT_FOUND, KEYWORD_INVALID, KEYWORD_FOUND};
 int findkwd(param_pointer p, const char *name, int *result, const char *keyword, int value, ...)
 {
     const char *word;
+    char wordbuf[INI_MAX_LINELEN];
     va_list ap;
     const char *kwds[MAX_KWD], **s;
     int nargs = 0;
 
-    if ((word = iniFind(p->fp, name, p->section)) == NULL)
+    if ((word = iniFindString(p->fp, name, p->section, wordbuf, sizeof(wordbuf))) == NULL)
 	return NAME_NOT_FOUND;
 
     kwds[nargs++] = keyword;
@@ -431,6 +432,7 @@ int findkwd(param_pointer p, const char *name, int *result, const char *keyword,
 int read_ini(param_pointer p)
 {
     const char *s;
+    char sbuf[INI_MAX_LINELEN];
     double f;
     int value;
 
@@ -447,10 +449,10 @@ int read_ini(param_pointer p)
 	iniFindInt(p->fp, "PORT", p->section, &p->tcp_portno);
 	iniFindInt(p->fp, "RECONNECT_DELAY", p->section, &p->reconnect_delay);
 
-	if ((s = iniFind(p->fp, "TCPDEST", p->section))) {
+	if ((s = iniFindString(p->fp, "TCPDEST", p->section, sbuf, sizeof(sbuf)))) {
 	    p->tcp_destip = strdup(s);
 	}
-	if ((s = iniFind(p->fp, "DEVICE", p->section))) {
+	if ((s = iniFindString(p->fp, "DEVICE", p->section, sbuf, sizeof(sbuf)))) {
 	    p->device = strdup(s);
 	}
 	if (iniFindDouble(p->fp, "RESPONSE_TIMEOUT", p->section, &f)) {
@@ -478,10 +480,10 @@ int read_ini(param_pointer p)
 		    (void *)NULL) == KEYWORD_INVALID)
 	    return -1;
 #else
-	if (iniFind(p->fp, "RTS_MODE", p->section) != NULL) {
+	if (iniFindString(p->fp, "RTS_MODE", p->section, sbuf, sizeof(sbuf)) != NULL) {
 	    fprintf(stderr,"%s: warning - the RTS_MODE feature is not available with the installed libmodbus version (%s).\n"
 		    "to enable it, uninstall libmodbus-dev and rebuild with "
-		    "libmodbus built http://github.com/stephane/libmodbus:master .\n", 
+		    "libmodbus built http://github.com/stephane/libmodbus:master .\n",
 		    LIBMODBUS_VERSION_STRING, p->progname);
 	}
 #endif

src/hal/utils/halcmd.c

@@ -46,7 +46,7 @@
 #include "emc/linuxcnc.h"
 
 #ifndef NO_INI
-#include "inifile.h"		/* iniFind() from libnml */
+#include "inifile.h"		/* iniFindString() from libnml */
 FILE *halcmd_inifile = NULL;
 #endif
 
@@ -707,7 +707,7 @@ static int replace_vars(char *source_str, char *dest_str, int max_chars, char **
 {
     int retval = 0;
     int next_delim, remaining, buf_space;
-    char *replacement, sec[128], var[128];
+    char *replacement, sec[128], var[128], ini_buf[INI_MAX_LINELEN];
     static char info[256];
     char *sp=source_str, *dp=dest_str, *secP, *varP;
     const char 
@@ -776,11 +776,12 @@ static int replace_vars(char *source_str, char *dest_str, int max_chars, char **
 		var[next_delim]='\0';
 		if ( strlen(sec) > 0 ) {
 		/* get value from INI file */
-		/* cast to char ptr, we are discarding the 'const' */
-		    replacement = (char *) iniFind(halcmd_inifile, var, sec);
+		    replacement = (char *) iniFindString(halcmd_inifile, var, sec,
+		                                         ini_buf, sizeof(ini_buf));
 		} else {
 		/* no section specified */
-		    replacement = (char *) iniFind(halcmd_inifile, var, NULL);
+		    replacement = (char *) iniFindString(halcmd_inifile, var, NULL,
+		                                         ini_buf, sizeof(ini_buf));
 		}
 		if (replacement==NULL) {
                     *detail = info;

src/hal/utils/halrmt.c

@@ -303,12 +303,6 @@
 #include <rtapi_string.h>	// rtapi_strlcpy
 #include "hal.h"		// HAL public API decls
 #include "../hal_priv.h"	// private HAL decls
-/* non-EMC related uses of halrmt may want to avoid libnml dependency
-#ifndef NO_INI
-#include "inifile.h"		// iniFind() from libnml
-#endif
-#include <rtapi_string.h>
-*/
 
 /***********************************************************************
 *                  LOCAL FUNCTION DECLARATIONS                         *

src/libnml/inifile/inifile.cc

@@ -592,19 +592,22 @@ IniFile::Exception::Print(FILE *fp)
 
 
 extern "C" const char *
-iniFind(FILE *fp, const char *tag, const char *section)
+iniFindString(FILE *fp, const char *tag, const char *section,
+              char *buf, size_t bufsize)
 {
-    IniFile                     f(false, fp);
-
-    // Note: Using static storage for C API backward compatibility.
-    // This preserves the original non-reentrant behavior of the C API.
-    // The returned pointer is only valid until the next call.
-    // Callers needing to preserve the value should copy it immediately.
-    static std::string result_storage;
-    auto result = f.Find(tag, section);
+    IniFile f(false, fp);
+    auto result = f.FindString(buf, bufsize, tag, section);
     if (!result) return nullptr;
-    result_storage = *result;
-    return result_storage.c_str();
+    return *result;
+}
+
+extern "C" const char *
+iniFind(FILE *fp, const char *tag, const char *section)
+{
+    // Deprecated: This function uses static storage and is not reentrant.
+    // Use iniFindString() instead for thread-safe operation.
+    static char result_storage[LINELEN];
+    return iniFindString(fp, tag, section, result_storage, sizeof(result_storage));
 }
 
 extern "C" int

src/libnml/inifile/inifile.h

@@ -25,7 +25,13 @@ extern "C"
 {
 #endif
 
-extern const char *iniFind(FILE *fp, const char *tag, const char *section);
+// Recommended buffer size for iniFindString()
+#define INI_MAX_LINELEN 256
+
+extern const char *iniFind(FILE *fp, const char *tag, const char *section)
+    __attribute__((deprecated("use iniFindString() instead")));
+extern const char *iniFindString(FILE *fp, const char *tag, const char *section,
+                                 char *buf, size_t bufsize);
 extern int iniFindInt(FILE *fp, const char *tag, const char *section, int *result);
 extern int iniFindDouble(FILE *fp, const char *tag, const char *section, double *result);
 extern int TildeExpansion(const char *file, char *path, size_t size);