fix -Wshadow and -Wimplicit-int-conversion warnings

Author: ZERICO2005

src/crt/lltof.c

@@ -4,7 +4,7 @@
 
 float _lltof_c(long long x)
 {
-    uint8_t exponent = x ? __builtin_clrsbll(x) : LLONG_WIDTH - 1;
+    uint8_t exponent = x ? ((uint8_t)__builtin_clrsbll(x)) : LLONG_WIDTH - 1;
     if (exponent >= LLONG_WIDTH - LONG_WIDTH) {
         return (float)((long)x);
     }

src/crt/ulltof.c

@@ -4,7 +4,7 @@
 
 float _ulltof_c(unsigned long long x)
 {
-    uint8_t exponent = x ? __builtin_clzll(x) : ULLONG_WIDTH;
+    uint8_t exponent = x ? ((uint8_t)__builtin_clzll(x)) : ULLONG_WIDTH;
     if (exponent >= ULLONG_WIDTH - ULONG_WIDTH) {
         return (float)((unsigned long)x);
     }

src/libc/fgets.c

@@ -18,7 +18,7 @@ char* __attribute__((weak)) fgets(char *__restrict str, int num, FILE *__restric
         {
             break;
         }
-        *p++ = c;
+        *p++ = (char)c;
         if (c == '\n')
         {
             break;

src/libc/float64_rounding.c

@@ -75,7 +75,7 @@ long long llroundl(long double x) {
     FE_UPWARD     == softfloat_round_max)
 
 // assumes fenv.h macros match softfloat_roundingModes
-#define GET_FENV_SOFTFLOAT_ROUNDING() (fegetround())
+#define GET_FENV_SOFTFLOAT_ROUNDING() ((uint_fast8_t)fegetround())
 
 #else
     static uint_fast8_t GET_FENV_SOFTFLOAT_ROUNDING(void) {

src/libc/fread.c

@@ -24,7 +24,7 @@ size_t __attribute__((weak)) fread(void *ptr, size_t size, size_t count, FILE *_
             {
                 break;
             }
-            *p++ = c;
+            *p++ = (char)c;
         }
 
         return count;

src/libc/gmtime.c

@@ -82,7 +82,7 @@ struct tm *gmtime(const time_t *tp)
         tm2.tm_min++;
     }
 
-    tm2.tm_sec = t;
+    tm2.tm_sec = (int)t;
 
     return &tm2;
 }

src/libc/printf/nanoprintf.c

@@ -18,7 +18,7 @@
 
 static void npf_putc_std(int c, void *ctx) {
   (void)ctx;
-  outchar(c);
+  outchar((char)c);
 }
 
 static void npf_fputc_std(int c, void *ctx) {

src/libc/printf/nanoprintf.h

@@ -766,9 +766,9 @@ static npf_cnt_putc_ctx_t pc_cnt;
 #endif
 
 static void npf_putc_cnt(int c, void *ctx) {
-  npf_cnt_putc_ctx_t *pc_cnt = (npf_cnt_putc_ctx_t *)ctx;
-  ++pc_cnt->n;
-  pc_cnt->pc(c, pc_cnt->ctx); // sibling-call optimization
+  npf_cnt_putc_ctx_t *pc_putc_cnt = (npf_cnt_putc_ctx_t *)ctx;
+  ++pc_putc_cnt->n;
+  pc_putc_cnt->pc(c, pc_putc_cnt->ctx); // sibling-call optimization
 }
 
 #ifdef NANOPRINTF_STATIC_GLOBALS

src/libc/strftime.c

@@ -81,7 +81,7 @@ size_t strftime(char *__restrict s, size_t n, const char *__restrict f, const st
 
     while (s + 1 < e && *f)
     {
-        int c = *f++;
+        char c = *f++;
         int val;
 
         if (c != '%')