translate-c fails on macro with assert(1 && "error message")

[travisstaloch]

Zig Version

0.11.0-dev.1577+11cc1c16f

Steps to Reproduce and Observed Behavior

Sorry if this is a duplicate issue. Seems like it might be. I didn't find anything in a quick search.

It is common in c to provide an error message like this:

// /tmp/tmp.h
#include <assert.h>

#define FOO assert(1 && "error message")

a minimal @cImport in zig:

// /tmp/tmp.zig
const c = @cImport(@cInclude("tmp.h"));

test {
    _ = c;
}

Yields this error:

$ zig test -lc /tmp/tmp.zig -I/tmp
/home/travis/.cache/zig/o/581a6a5a6944f09e8260e88f89c213da/cimport.zig:616:66: error: cannot compare strings with !=
pub const FOO = assert((@as(c_int, 1) != 0) and ("error message" != 0));
                                                 ~~~~~~~~~~~~~~~~^~~~
/tmp/tmp.zig:1:11: error: C import failed: AnalysisFail
const c = @cImport(@cInclude("tmp.h"));
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
referenced by:
    test_0: /tmp/tmp.zig:4:9
    remaining reference traces hidden; use '-freference-trace' to see all reference traces

Expected Behavior

not sure what should happen. this IS a hacky way to show error messages. i'm only reporting it because its common in c.

[rohlem]

not sure what should happen.

IIUC pointers in boolean expressions in C are checked against 0 (= the null pointer constant).
I believe if the emitted Zig code was similarly != null instead of != 0 for pointers (which string literals yield), that would solve the issue.

[travisstaloch]

I believe if the emitted Zig code was similarly != null instead of != 0 for pointers (which string literals yield), that would solve the issue.

Its not possible to compare a string literal with null. It would need to be first cast ie @ptrCast([*c]const u8, "error message). Perhaps another type of pointer would be better, not sure.

Of course, this assumes that translate-c can detect when a string literal is being compared using an equality operator. And I don't know that this is true.

[easeaico]

Does anyone know how to fix this problem?

[Vexu]

Yes, something like this should do it:

diff --git a/src/translate_c.zig b/src/translate_c.zig
index ab48ee1f5..c77576cb0 100644
--- a/src/translate_c.zig
+++ b/src/translate_c.zig
@@ -5969,6 +5969,9 @@ fn macroIntToBool(c: *Context, node: Node) !Node {
     if (isBoolRes(node)) {
         return node;
     }
+    if (node.tag() == .string_literal) {
+        return Tag.true_literal.init();
+    }
 
     return Tag.not_equal.create(c.arena, .{ .lhs = node, .rhs = Tag.zero_literal.init() });
 }

[VoilaNeighbor]

When is this going to be merged? Seems like translate-c is already producing a comparison with pointers but that still does not work with string literals.

A real world example with cglm:

/*!
 * @brief mupliply N mat4 matrices and store result in dest
 *
 * this function lets you multiply multiple (more than two or more...) matrices
 * <br><br>multiplication will be done in loop, this may reduce instructions
 * size but if <b>len</b> is too small then compiler may unroll whole loop,
 * usage:
 * @code
 * mat m1, m2, m3, m4, res;
 *
 * glm_mat4_mulN((mat4 *[]){&m1, &m2, &m3, &m4}, 4, res);
 * @endcode
 *
 * @warning matrices parameter is pointer array not mat4 array!
 *
 * @param[in]  matrices mat4 * array
 * @param[in]  len      matrices count
 * @param[out] dest     result
 */
CGLM_INLINE
void
glm_mat4_mulN(mat4 * __restrict matrices[], uint32_t len, mat4 dest) {
  uint32_t i;

#ifndef NDEBUG
  assert(len > 1 && "there must be least 2 matrices to go!");
#endif

  glm_mat4_mul(*matrices[0], *matrices[1], dest);

  for (i = 2; i < len; i++)
    glm_mat4_mul(dest, *matrices[i], dest);
}

Translated:

pub inline fn glm_mat4_mulN(arg_matrices: [*c][*c]mat4, arg_len: u32, arg_dest: [*c]vec4) void {
    var matrices = arg_matrices;
    _ = &matrices;
    var len = arg_len;
    _ = &len;
    var dest = arg_dest;
    _ = &dest;
    var i: u32 = undefined;
    _ = &i;
    _ = !!((len > @as(u32, @bitCast(@as(c_int, 1)))) and ("there must be least 2 matrices to go!" != null)) or ((blk: {
        _assert("len > 1 && \"there must be least 2 matrices to go!\"", "C:\\Users\\BaiDongJie\\Custom\\Project\\FIG-dual\\lib\\cglm-v0.9.4/mat4.h", @as(c_uint, @bitCast(@as(c_int, 380))));
        break :blk @as(c_int, 0);
    }) != 0);
    glm_mat4_mul(@as([*c]vec4, @ptrCast(@alignCast(&matrices[@as(c_uint, @intCast(@as(c_int, 0)))].*))), @as([*c]vec4, @ptrCast(@alignCast(&matrices[@as(c_uint, @intCast(@as(c_int, 1)))].*))), dest);
    {
        i = 2;
        while (i < len) : (i +%= 1) {
            glm_mat4_mul(dest, @as([*c]vec4, @ptrCast(@alignCast(&matrices[i].*))), dest);
        }
    }
}

[travisstaloch]

Yes, something like this should do it:

diff --git a/src/translate_c.zig b/src/translate_c.zig
index ab48ee1f5..c77576cb0 100644
--- a/src/translate_c.zig
+++ b/src/translate_c.zig
@@ -5969,6 +5969,9 @@ fn macroIntToBool(c: *Context, node: Node) !Node {
     if (isBoolRes(node)) {
         return node;
     }
+    if (node.tag() == .string_literal) {
+        return Tag.true_literal.init();
+    }
 
     return Tag.not_equal.create(c.arena, .{ .lhs = node, .rhs = Tag.zero_literal.init() });
 }

@Vexu I applied your patch and it does indeed work, producing the following

...
pub const FOO = assert((@as(c_int, 0) != 0) and true);

when given

#include <assert.h>

#define FOO assert(0 && "error message")

As you can see, "error message" gets lost. Do you think it would be better to preserve the string literal, maybe translating it as the following instead of true?

@intFromPtr("error message") != 0

[travisstaloch]

as mentioned by @rohlem above, I noticed that the following produces invalid zig code, comparing a str literal with null

// /tmp/tmp.h
void foo() { if(0 && "error message") {} }

$ zig translate-c /tmp/tmp.h

result:

pub export fn foo() void {
    if (false and ("error message" != null)) {}
}

Should this be supported? If so, any idea how to fix it? I searched around in src/translate_c.zig a bit but not sure how this might be done.

[Vexu]

Try here:

zig/src/translate_c.zig

Lines 2088 to 2091 in f7a76bd

	.Pointer => {
	// node != null
	return Tag.not_equal.create(c.arena, .{ .lhs = node, .rhs = Tag.null_literal.init() });
	},

[travisstaloch]

thanks @Vexu will work on this tomorrow. will make a separate pr unless you think i should just add it #19610.

[travisstaloch]

Try here:

zig/src/translate_c.zig

Lines 2088 to 2091 in f7a76bd

	.Pointer => {
	// node != null
	return Tag.not_equal.create(c.arena, .{ .lhs = node, .rhs = Tag.null_literal.init() });
	},

just submitted #19625 with a fix at this location