241201.1 · 0b82b3841b05faefe0ac18379bdb361b7e4e3464

builtin.c: typecheck builtin cfunctions in function_list

In C23 (default C standard used by GCC 15), jv (*fptr)(); has become equivalent to jv (*fptr)(void); so we can no longer assign builtin implemenations directly to the fptr member of cfunctions without generating a compile error.

Since there does not seem to be any straight-forward way to tell autoconf to force the compiler to use C99 short of explicitly adding -std=c99 to CFLAGS, it is probably a cleaner solution to just make the code C23 compatible.

A possible solution could have been to just redeclare cfunction.fptr as void*, but then the functions' return type would not have been type checked (e.g. if you tried to add a {printf, "printf", 2}, where printf is a function that does not return jv, the compiler wouldn't have complained.) We were already not typechecking the arguments of the functions, so e.g.
{binop_plus, "_plus", 3}, /* instead of {f_plus, "_plus, 3}, */
{f_setpath, "setpath", 4}, /* instead of {f_setpath, "setpath", 3}, */ compile without errors despite not having the correct prototype.

So I thought of instead improving the situation by redefining cfunction.fptr as a union of function pointers with the prototypes that the jq bytecode interpreter can call, and use a macro to add the builtin functions to function_list using to the arity argument to assign the implementation function to the appropriate union member.

Now the code won't compile if the wrong arity, or an arity not supported by the bytecode interpreter (>5 = 1input+4arguments), or a prototype not jallable by the bytecode interpreter (e.g. binop_plus that doesn't expect a jq_state* argument).

Also, the code now compiles with gcc -std=c23.

Fixes #3206

@@ -2,7 +2,7 @@ #define BYTECODE_H #include <stdint.h> -#include "jv.h"+#include "jq.h"  typedef enum { #define OP(name, imm, in, out) name,@@ -44,9 +44,14 @@ struct opcode_description { const struct opcode_description* opcode_describe(opcode op);  -#define MAX_CFUNCTION_ARGS 10+#define MAX_CFUNCTION_ARGS 4 struct cfunction {-  jv (*fptr)();+  union {+    jv (*a1)(jq_state *, jv);+    jv (*a2)(jq_state *, jv, jv);+    jv (*a3)(jq_state *, jv, jv, jv);+    jv (*a4)(jq_state *, jv, jv, jv, jv);+  } fptr;   const char* name;   int nargs; };