[PATCH 0/1] MR10107: msvcrt: Ignore negative precision for float args in printf().

[eric pouech (＠epo)]

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=59403

Signed-off-by: Eric Pouech <[e-mail]>

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10107

[PATCH 1/1] msvcrt: Ignore negative precision for float args in printf().

[Eric Pouech]

From: Eric Pouech <[e-mail]>

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=59403

Signed-off-by: Eric Pouech <[e-mail]>
---
 dlls/msvcrt/printf.h       | 4 ++--
 dlls/msvcrt/tests/printf.c | 8 ++++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/dlls/msvcrt/printf.h b/dlls/msvcrt/printf.h
index be30d6ae719..cfcfd5be771 100644
--- a/dlls/msvcrt/printf.h
+++ b/dlls/msvcrt/printf.h
@@ -375,7 +375,7 @@ static inline int FUNC_NAME(pf_output_special_fp)(FUNC_NAME(puts_clbk) pf_puts,
     if(!flags->Alternate && (flags->Format == 'g' || flags->Format == 'G')) sfx_len = frac_len;
     else sfx_len = flags->Precision;
 
-    if(sfx_len == -1) {
+    if(sfx_len < 0) {
         if(strchr("fFeE", flags->Format)) sfx_len = 6;
         else if(flags->Format == 'a' || flags->Format == 'A') sfx_len = 13;
     }
@@ -614,7 +614,7 @@ static inline int FUNC_NAME(pf_output_fp)(FUNC_NAME(puts_clbk) pf_puts, void *pu
     ULONGLONG m;
     DWORD l;
 
-    if(flags->Precision == -1)
+    if(flags->Precision < 0)
         flags->Precision = 6;
 
     v = frexp(v, &e2);
diff --git a/dlls/msvcrt/tests/printf.c b/dlls/msvcrt/tests/printf.c
index dc0038b3372..c21b1285275 100644
--- a/dlls/msvcrt/tests/printf.c
+++ b/dlls/msvcrt/tests/printf.c
@@ -377,6 +377,14 @@ static void test_sprintf( void )
     ok(!strcmp(buffer,"foo  "),"Negative field width ignored \"%s\"\n",buffer);
     ok( r==5, "return count wrong\n");
 
+    r = p_sprintf(buffer, "%.*f", 0x80000000, 3.14);
+    ok(!strcmp(buffer,"3.140000"),"Negative precision ignored \"%s\"\n",buffer);
+    ok( r==8, "return count wrong\n");
+
+    r = p_sprintf(buffer, "%.*f", 0x80000000, NAN);
+    ok(!strcmp(buffer,"1.#QNAN0"),"Negative precision ignored \"%s\"\n",buffer);
+    ok( r==8, "return count wrong\n");
+
     x = 0;
     r = p_sprintf(buffer, "asdf%n", &x );
     if (r == -1)
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/10107

[Paul Gofman (＠gofman)]

Paul Gofman (@gofman) commented about dlls/msvcrt/tests/printf.c:
> ok(!strcmp(buffer,"foo  "),"Negative field width ignored \"%s\"\n",buffer);
>      ok( r==5, "return count wrong\n");
>
> +    r = p_sprintf(buffer, "%.*f", 0x80000000, 3.14);
> +    ok(!strcmp(buffer,"3.140000"),"Negative precision ignored \"%s\"\n",buffer);
> +    ok( r==8, "return count wrong\n");
> +
> +    r = p_sprintf(buffer, "%.*f", 0x80000000, NAN);

Does it really ignore it or maybe uses just some bits, or checks maximum value (what will it do for 0x7fffffff?) or maybe even that 0x80000000 is meaningful undocuemnted flag? I'd suggest to extend the test with some other values, like 0x80000001 for a start and overall check for more values, even if locally not to overload the test suite with paranoid checks for any possible condition.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10107#note_129704

[eric pouech (＠epo)]

On Sat Feb 14 17:46:19 2026 +0000, Paul Gofman wrote:
> Does it really ignore it or maybe uses just some bits, or checks maximum
> value (what will it do for 0x7fffffff?) or maybe even that 0x80000000 is
> meaningful undocuemnted flag? I'd suggest to extend the test with some
> other values, like 0x80000001 for a start and overall check for more
> values, even if locally not to overload the test suite with paranoid
> checks for any possible condition.
> I actually tested on Win10 all precision values in \[-64k,-1\], \[INT_MIN, INT_MIN+64k\] and \[INT_MIN, -1\] by 0x1000 step and all behave the same

I'm not sure it's worth extending the tests

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10107#note_129708

[PATCH 0/1] MR10107: msvcrt: Ignore negative precision for float args in printf(). - approved

[Piotr Caban (＠piotr)]

This merge request was approved by Piotr Caban.
-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10107