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build: Fix warnings about control paths #5806

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Build: Fix warnings about control paths
HuidaeCho May 31, 2025
ece09a4
Merge branch 'main' into control_paths
echoix Oct 22, 2025
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2 changes: 2 additions & 0 deletions lib/arraystats/class.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,8 @@ int AS_option_to_algorithm(const struct Option *option)
return CLASS_DISCONT;

G_fatal_error(_("Unknown algorithm '%s'"), option->answer);

return 0;
}

double AS_class_apply_algorithm(int algo, const double data[], int nrec,
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2 changes: 2 additions & 0 deletions lib/gis/parser_dependencies.c
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Expand Up @@ -124,6 +124,8 @@ static int is_flag(const void *p)
}

G_fatal_error(_("Internal error: option or flag not found"));

return -1;
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@echoix echoix May 31, 2025

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I know this is under a G_fatal_error, so shouldn't be reached. But the 4 usages of this function in this file only check with if (is_flag(p)) {}, so a non-zero value, here -1, doesn't mean the same.

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@nilason nilason Jun 1, 2025

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Code after G_fatal_error is never reached and thus unnecessary. (Competent static analysers recognises this too).

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@HuidaeCho HuidaeCho Jun 2, 2025

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I know this is under a G_fatal_error, so shouldn't be reached. But the 4 usages of this function in this file only check with if (is_flag(p)) {}, so a non-zero value, here -1, doesn't mean the same.

You're right. We could do if (is_flag(p) == 1), but again, we'll never reach return -1 anyway. It's just there to suppress the warning.

}

static int is_present(const void *p)
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7 changes: 4 additions & 3 deletions ps/ps.map/scale.c
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Expand Up @@ -17,9 +17,9 @@
static double do_scale(char *);

#ifdef __GNUC_MINOR__
static int OOPS(void) __attribute__((__noreturn__));
static void OOPS(void) __attribute__((__noreturn__));
#else
static int OOPS();
static void OOPS();
#endif

double scale(char *text)
Expand Down Expand Up @@ -131,9 +131,10 @@ static double do_scale(char *text)
return METERS_TO_INCHES * distance(PS.w.east, PS.w.west) * u1 / u2;
}
OOPS();
return 0;
}

static int OOPS(void)
static void OOPS(void)
{
G_fatal_error(_("PSmap: do_scale(): shouldn't happen"));
}
2 changes: 1 addition & 1 deletion raster/r.li/r.li.daemon/avl.c
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Expand Up @@ -208,7 +208,6 @@ static avl_node *avl_individua(const avl_tree root, const generic_cell k,
switch (ris) {
case GC_EQUAL: {
return root;
break;
}
case GC_HIGHER: {
*father = root;
Expand All @@ -227,6 +226,7 @@ static avl_node *avl_individua(const avl_tree root, const generic_cell k,
G_fatal_error("\avl.c: avl_individua: error");
}
}
return NULL;
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@nilason nilason Jun 1, 2025

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This is also never reached. I wonder how you triggered these warnings?

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@HuidaeCho HuidaeCho Jun 2, 2025

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I think MSVC reports these warnings by default:

C:\Users\hcho\usr\grass\grass\raster\r.li\r.li.daemon\avl.c(230,1): warning C4715: 'avl_individua': not all control paths return a value [C:\Users\hcho\usr\grass\grass\build27\raster\r.li\grass_rli.vcxproj]

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@HuidaeCho HuidaeCho Jun 2, 2025

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https://learn.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-1-c4715?view=msvc-170

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@echoix echoix Jun 3, 2025

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At the end of that page, it points ta a link that shows how to use __declspec(noreturn) to annotate a function that never returns, for that analysis.

https://learn.microsoft.com/en-us/cpp/cpp/noreturn?view=msvc-170

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@HuidaeCho HuidaeCho Jun 3, 2025

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That's for void functions technically. Or

It does not make sense for a noreturn function to have a return type other than void.

https://gcc.gnu.org/onlinedocs/gcc-3.4.3/gcc/Function-Attributes.html

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@nilason nilason Jun 10, 2025

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G_fatal_error is attributed with __attribute__((noreturn)):

grass/include/grass/defs/gis.h

Lines 312 to 313 in d129608

void G_fatal_error(const char *, ...) __attribute__((format(printf, 1, 2)))
__attribute__((noreturn));

maybe that needs an update for windows?

This is a very common practice (no return after G_fatal_error) in GRASS code, so this should be solved in a more general way.

Something like:

void G_fatal_error(const char *, ...) __attribute__((format(printf, 1, 2))) 
#if defined(_MSC_VER)
__declspec(noreturn);
#else
 __attribute__((noreturn));
#endif

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@nilason nilason Jun 11, 2025

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If my proposed change works, I'd suggest defining a macro in gis.h:

#if defined(_MSC_VER)
#define G_NORETURN __declspec(noreturn)
#else
#define G_NORETURN __attribute__((noreturn))
#endif

which then can be added:

void G_fatal_error(const char *, ...) __attribute__((format(printf, 1, 2))) G_NORETURN;

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@nilason nilason Jun 11, 2025

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Or using the C11 keyword _Noreturn 

#if  __STDC_VERSION__ < 202311L
#define G_NORETURN _Noreturn
#else
#define G_NORETURN [[noreturn]]
#endif

...

G_NORETURN void G_fatal_error(const char *, ...) __attribute__((format(printf, 1, 2)));

(untested)

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@nilason nilason Jun 11, 2025

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The _Noreturn suggestion above doesn't work well with C++, however this seems to work:

#if __STDC_VERSION__ < 202311L
#if defined(_MSC_VER)
#define G_NORETURN __declspec(noreturn)
#else
#define G_NORETURN __attribute__((noreturn))
#endif
#else
#define G_NORETURN [[noreturn]]
#endif

(The [[noreturn]] attribute is added to C23 as well as C++11).

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@wenzeslaus wenzeslaus Aug 21, 2025

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G_NORETURN seems reasonable to me although for the future plain [[noreturn]] would be preferable.

}

static int avl_height(const avl_tree root)
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