pg: Better error reporting + basic exec() method

c/libpq.h

@@ -0,0 +1,64 @@
+/* libpq is not being linked directly and there's no build-time dependency on it.
+ * This means we need to manually copy over some definitions from libpq-fe.h
+ */
+
+typedef struct PGconn PGconn;
+typedef struct PGresult PGresult;
+
+typedef enum {
+    PGRES_EMPTY_QUERY = 0, PGRES_COMMAND_OK, PGRES_TUPLES_OK, PGRES_COPY_OUT, PGRES_COPY_IN,
+    PGRES_BAD_RESPONSE, PGRES_NONFATAL_ERROR, PGRES_FATAL_ERROR,  PGRES_COPY_BOTH,
+    PGRES_SINGLE_TUPLE, PGRES_PIPELINE_SYNC, PGRES_PIPELINE_ABORTED, PGRES_TUPLES_CHUNK
+} ExecStatusType;
+typedef enum { PQERRORS_TERSE, PQERRORS_DEFAULT, PQERRORS_VERBOSE, PQERRORS_SQLSTATE } PGVerbosity;
+typedef enum { PQSHOW_CONTEXT_NEVER, PQSHOW_CONTEXT_ERRORS, PQSHOW_CONTEXT_ALWAYS } PGContextVisibility;
+
+#define PG_DIAG_SEVERITY        'S'
+#define PG_DIAG_SEVERITY_NONLOCALIZED 'V'
+#define PG_DIAG_SQLSTATE        'C'
+#define PG_DIAG_MESSAGE_PRIMARY 'M'
+#define PG_DIAG_MESSAGE_DETAIL  'D'
+#define PG_DIAG_MESSAGE_HINT    'H'
+#define PG_DIAG_STATEMENT_POSITION 'P'
+#define PG_DIAG_INTERNAL_POSITION 'p'
+#define PG_DIAG_INTERNAL_QUERY  'q'
+#define PG_DIAG_CONTEXT         'W'
+#define PG_DIAG_SCHEMA_NAME     's'
+#define PG_DIAG_TABLE_NAME      't'
+#define PG_DIAG_COLUMN_NAME     'c'
+#define PG_DIAG_DATATYPE_NAME   'd'
+#define PG_DIAG_CONSTRAINT_NAME 'n'
+#define PG_DIAG_SOURCE_FILE     'F'
+#define PG_DIAG_SOURCE_LINE     'L'
+#define PG_DIAG_SOURCE_FUNCTION 'R'
+
+#define PG_FUNCS \
+    X(PQclear, void, PGresult *) \
+    X(PQconnectdb, PGconn *, const char *) \
+    X(PQcmdTuples, char *, PGresult *) \
+    X(PQerrorMessage, char *, const PGconn *) \
+    X(PQexec, PGresult *, PGconn *, const char *) \
+    X(PQfinish, void, PGconn *) \
+    X(PQfreemem, void, void *) \
+    X(PQlibVersion, int, void) \
+    X(PQresStatus, char *, ExecStatusType) \
+    X(PQresultErrorField, char *, const PGresult *, int) \
+    X(PQresultErrorMessage, char *, const PGresult *res) \
+    X(PQresultStatus, ExecStatusType, const PGresult *) \
+    X(PQresultVerboseErrorMessage, char *, const PGresult *, PGVerbosity, PGContextVisibility) \
+    X(PQserverVersion, int, const PGconn *) \
+    X(PQstatus, int, const PGconn *)
+
+#define X(n, r, ...) static r (*n)(__VA_ARGS__);
+PG_FUNCS
+#undef X
+
+static void fupg_load() {
+    void *handle = dlopen("libpq.so", RTLD_LAZY);
+    if (!handle) croak("Unable to load libpq: %s", dlerror());
+#define X(n, ...) if (!(n = dlsym(handle, #n))) croak("Unable to load libpq: %s", dlerror());
+PG_FUNCS
+#undef X
+}
+
+#undef PG_FUNCS