diff --git a/src/glsl/pp/sl_pp_context.c b/src/glsl/pp/sl_pp_context.c
index 88a002c1c73..b196d8102a0 100644
--- a/src/glsl/pp/sl_pp_context.c
+++ b/src/glsl/pp/sl_pp_context.c
@@ -85,6 +85,7 @@ sl_pp_context_add_unique_str(struct sl_pp_context *context,
    }
 
    if (!context->cstr_pool) {
+      strcpy(context->error_msg, "out of memory");
       return -1;
    }
 
diff --git a/src/glsl/pp/sl_pp_context.h b/src/glsl/pp/sl_pp_context.h
index 5826f9448d0..8bed1420454 100644
--- a/src/glsl/pp/sl_pp_context.h
+++ b/src/glsl/pp/sl_pp_context.h
@@ -47,7 +47,7 @@ struct sl_pp_context {
 
    unsigned int if_stack[SL_PP_MAX_IF_NESTING];
    unsigned int if_ptr;
-   int if_value;
+   unsigned int if_value;
 
    char error_msg[SL_PP_MAX_ERROR_MSG];
 
diff --git a/src/glsl/pp/sl_pp_define.c b/src/glsl/pp/sl_pp_define.c
index 9bc9fb53599..391178aa696 100644
--- a/src/glsl/pp/sl_pp_define.c
+++ b/src/glsl/pp/sl_pp_define.c
@@ -41,7 +41,8 @@ skip_whitespace(const struct sl_pp_token_info *input,
 
 
 static int
-_parse_formal_args(const struct sl_pp_token_info *input,
+_parse_formal_args(struct sl_pp_context *context,
+                   const struct sl_pp_token_info *input,
                    unsigned int *first,
                    unsigned int last,
                    struct sl_pp_macro *macro)
@@ -57,7 +58,7 @@ _parse_formal_args(const struct sl_pp_token_info *input,
          return 0;
       }
    } else {
-      /* Expected either an identifier or `)'. */
+      strcpy(context->error_msg, "expected either an identifier or `)'");
       return -1;
    }
 
@@ -65,12 +66,13 @@ _parse_formal_args(const struct sl_pp_token_info *input,
 
    for (;;) {
       if (*first < last && input[*first].token != SL_PP_IDENTIFIER) {
-         /* Expected an identifier. */
+         strcpy(context->error_msg, "expected an identifier");
          return -1;
       }
 
       *arg = malloc(sizeof(struct sl_pp_macro_formal_arg));
       if (!*arg) {
+         strcpy(context->error_msg, "out of memory");
          return -1;
       }
 
@@ -90,14 +92,16 @@ _parse_formal_args(const struct sl_pp_token_info *input,
             (*first)++;
             return 0;
          } else {
-            /* Expected either `,' or `)'. */
+            strcpy(context->error_msg, "expected either `,' or `)'");
             return -1;
          }
       } else {
-         /* Expected either `,' or `)'. */
+         strcpy(context->error_msg, "expected either `,' or `)'");
          return -1;
       }
    }
+
+   /* Should not gete here. */
 }
 
 
@@ -118,6 +122,7 @@ sl_pp_process_define(struct sl_pp_context *context,
       first++;
    }
    if (macro_name == -1) {
+      strcpy(context->error_msg, "expected an identifier");
       return -1;
    }
 
@@ -130,6 +135,7 @@ sl_pp_process_define(struct sl_pp_context *context,
    if (!macro) {
       macro = sl_pp_macro_new();
       if (!macro) {
+         strcpy(context->error_msg, "out of memory");
          return -1;
       }
 
@@ -149,7 +155,7 @@ sl_pp_process_define(struct sl_pp_context *context,
     */
    if (first < last && input[first].token == SL_PP_LPAREN) {
       first++;
-      if (_parse_formal_args(input, &first, last, macro)) {
+      if (_parse_formal_args(context, input, &first, last, macro)) {
          return -1;
       }
    }
@@ -164,6 +170,7 @@ sl_pp_process_define(struct sl_pp_context *context,
 
    macro->body = malloc(sizeof(struct sl_pp_token_info) * body_len);
    if (!macro->body) {
+      strcpy(context->error_msg, "out of memory");
       return -1;
    }
 
diff --git a/src/glsl/pp/sl_pp_expression.c b/src/glsl/pp/sl_pp_expression.c
index a692430abbf..6b2329ed1a7 100644
--- a/src/glsl/pp/sl_pp_expression.c
+++ b/src/glsl/pp/sl_pp_expression.c
@@ -47,6 +47,7 @@ _parse_primary(struct parse_context *ctx,
       ctx->input++;
    } else {
       if (ctx->input->token != SL_PP_LPAREN) {
+         strcpy(ctx->context->error_msg, "expected `('");
          return -1;
       }
       ctx->input++;
@@ -54,6 +55,7 @@ _parse_primary(struct parse_context *ctx,
          return -1;
       }
       if (ctx->input->token != SL_PP_RPAREN) {
+         strcpy(ctx->context->error_msg, "expected `)'");
          return -1;
       }
       ctx->input++;
diff --git a/src/glsl/pp/sl_pp_if.c b/src/glsl/pp/sl_pp_if.c
index 90b80512375..44bbefa3577 100644
--- a/src/glsl/pp/sl_pp_if.c
+++ b/src/glsl/pp/sl_pp_if.c
@@ -59,7 +59,7 @@ _parse_defined(struct sl_pp_context *context,
    }
 
    if (input[*pi].token != SL_PP_IDENTIFIER) {
-      /* Identifier expected. */
+      strcpy(context->error_msg, "expected an identifier");
       return -1;
    }
 
@@ -75,7 +75,7 @@ _parse_defined(struct sl_pp_context *context,
    if (parens) {
       skip_whitespace(input, pi);
       if (input[*pi].token != SL_PP_RPAREN) {
-         /* `)' expected */
+         strcpy(context->error_msg, "expected `)'");
          return -1;
       }
       (*pi)++;
@@ -91,10 +91,15 @@ _parse_defined(struct sl_pp_context *context,
       return -1;
    }
 
-   return sl_pp_process_out(state, &result);
+   if (sl_pp_process_out(state, &result)) {
+      strcpy(context->error_msg, "out of memory");
+      return -1;
+   }
+
+   return 0;
 }
 
-static int
+static unsigned int
 _evaluate_if_stack(struct sl_pp_context *context)
 {
    unsigned int i;
@@ -119,7 +124,7 @@ _parse_if(struct sl_pp_context *context,
    int result;
 
    if (!context->if_ptr) {
-      /* #if nesting too deep. */
+      strcpy(context->error_msg, "`#if' nesting too deep");
       return -1;
    }
 
@@ -151,6 +156,7 @@ _parse_if(struct sl_pp_context *context,
 
       default:
          if (sl_pp_process_out(&state, &input[i])) {
+            strcpy(context->error_msg, "out of memory");
             free(state.out);
             return -1;
          }
@@ -160,6 +166,7 @@ _parse_if(struct sl_pp_context *context,
 
    eof.token = SL_PP_EOF;
    if (sl_pp_process_out(&state, &eof)) {
+      strcpy(context->error_msg, "out of memory");
       free(state.out);
       return -1;
    }
@@ -182,13 +189,13 @@ static int
 _parse_else(struct sl_pp_context *context)
 {
    if (context->if_ptr == SL_PP_MAX_IF_NESTING) {
-      /* No matching #if. */
+      strcpy(context->error_msg, "no matching `#if'");
       return -1;
    }
 
    /* Bit b1 indicates we already went through #else. */
    if (context->if_stack[context->if_ptr] & 2) {
-      /* No matching #if. */
+      strcpy(context->error_msg, "no matching `#if'");
       return -1;
    }
 
@@ -217,7 +224,7 @@ sl_pp_process_ifdef(struct sl_pp_context *context,
    unsigned int i;
 
    if (!context->if_ptr) {
-      /* #if nesting too deep. */
+      strcpy(context->error_msg, "`#if' nesting too deep");
       return -1;
    }
 
@@ -246,12 +253,12 @@ sl_pp_process_ifdef(struct sl_pp_context *context,
          break;
 
       default:
-         /* Expected an identifier. */
+         strcpy(context->error_msg, "expected an identifier");
          return -1;
       }
    }
 
-   /* Expected an identifier. */
+   strcpy(context->error_msg, "expected an identifier");
    return -1;
 }
 
@@ -264,7 +271,7 @@ sl_pp_process_ifndef(struct sl_pp_context *context,
    unsigned int i;
 
    if (!context->if_ptr) {
-      /* #if nesting too deep. */
+      strcpy(context->error_msg, "`#if' nesting too deep");
       return -1;
    }
 
@@ -293,12 +300,12 @@ sl_pp_process_ifndef(struct sl_pp_context *context,
          break;
 
       default:
-         /* Expected an identifier. */
+         strcpy(context->error_msg, "expected an identifier");
          return -1;
       }
    }
 
-   /* Expected an identifier. */
+   strcpy(context->error_msg, "expected an identifier");
    return -1;
 }
 
@@ -341,7 +348,7 @@ sl_pp_process_endif(struct sl_pp_context *context,
                     unsigned int last)
 {
    if (context->if_ptr == SL_PP_MAX_IF_NESTING) {
-      /* No matching #if. */
+      strcpy(context->error_msg, "no matching `#if'");
       return -1;
    }
 
diff --git a/src/glsl/pp/sl_pp_line.c b/src/glsl/pp/sl_pp_line.c
index a56417a8610..c38f4b0f2e6 100644
--- a/src/glsl/pp/sl_pp_line.c
+++ b/src/glsl/pp/sl_pp_line.c
@@ -29,31 +29,6 @@
 #include "sl_pp_process.h"
 
 
-static int
-_parse_integer(const char *input,
-               unsigned int *number)
-{
-   unsigned int n = 0;
-
-   while (*input >= '0' && *input <= '9') {
-      if (n * 10 < n) {
-         /* Overflow. */
-         return -1;
-      }
-
-      n = n * 10 + (*input++ - '0');
-   }
-
-   if (*input != '\0') {
-      /* Invalid decimal number. */
-      return -1;
-   }
-
-   *number = n;
-   return 0;
-}
-
-
 int
 sl_pp_process_line(struct sl_pp_context *context,
                    const struct sl_pp_token_info *input,
@@ -65,7 +40,6 @@ sl_pp_process_line(struct sl_pp_context *context,
    struct sl_pp_process_state state;
    int line_number = -1;
    int file_number = -1;
-   const char *str;
    unsigned int line;
 
    memset(&state, 0, sizeof(state));
@@ -84,6 +58,7 @@ sl_pp_process_line(struct sl_pp_context *context,
 
       default:
          if (sl_pp_process_out(&state, &input[i])) {
+            strcpy(context->error_msg, "out of memory");
             free(state.out);
             return -1;
          }
@@ -94,7 +69,7 @@ sl_pp_process_line(struct sl_pp_context *context,
    if (state.out_len > 0 && state.out[0].token == SL_PP_NUMBER) {
       line_number = state.out[0].data.number;
    } else {
-      strcpy(context->error_msg, "expected number after `#line'");
+      strcpy(context->error_msg, "expected a number after `#line'");
       free(state.out);
       return -1;
    }
@@ -103,13 +78,13 @@ sl_pp_process_line(struct sl_pp_context *context,
       if (state.out[1].token == SL_PP_NUMBER) {
          file_number = state.out[1].data.number;
       } else {
-         strcpy(context->error_msg, "expected number after line number");
+         strcpy(context->error_msg, "expected a number after line number");
          free(state.out);
          return -1;
       }
 
       if (state.out_len > 2) {
-         strcpy(context->error_msg, "expected end of line after file number");
+         strcpy(context->error_msg, "expected an end of line after file number");
          free(state.out);
          return -1;
       }
@@ -117,10 +92,7 @@ sl_pp_process_line(struct sl_pp_context *context,
 
    free(state.out);
 
-   str = sl_pp_context_cstr(context, line_number);
-   if (_parse_integer(str, &line)) {
-      return -1;
-   }
+   line = atoi(sl_pp_context_cstr(context, line_number));
 
    if (context->line != line) {
       struct sl_pp_token_info ti;
@@ -128,6 +100,7 @@ sl_pp_process_line(struct sl_pp_context *context,
       ti.token = SL_PP_LINE;
       ti.data.line = line;
       if (sl_pp_process_out(pstate, &ti)) {
+         strcpy(context->error_msg, "out of memory");
          return -1;
       }
 
@@ -137,10 +110,7 @@ sl_pp_process_line(struct sl_pp_context *context,
    if (file_number != -1) {
       unsigned int file;
 
-      str = sl_pp_context_cstr(context, file_number);
-      if (_parse_integer(str, &file)) {
-         return -1;
-      }
+      file_number = atoi(sl_pp_context_cstr(context, file_number));
 
       if (context->file != file) {
          struct sl_pp_token_info ti;
@@ -148,6 +118,7 @@ sl_pp_process_line(struct sl_pp_context *context,
          ti.token = SL_PP_FILE;
          ti.data.file = file;
          if (sl_pp_process_out(pstate, &ti)) {
+            strcpy(context->error_msg, "out of memory");
             return -1;
          }
 
diff --git a/src/glsl/pp/sl_pp_macro.c b/src/glsl/pp/sl_pp_macro.c
index d14c9825557..7793562781f 100644
--- a/src/glsl/pp/sl_pp_macro.c
+++ b/src/glsl/pp/sl_pp_macro.c
@@ -107,7 +107,12 @@ _out_number(struct sl_pp_context *context,
 
    ti.token = SL_PP_NUMBER;
    ti.data.number = sl_pp_context_add_unique_str(context, buf);
-   return sl_pp_process_out(state, &ti);
+   if (sl_pp_process_out(state, &ti)) {
+      strcpy(context->error_msg, "out of memory");
+      return -1;
+   }
+
+   return 0;
 }
 
 int
@@ -125,6 +130,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
    unsigned int j;
 
    if (input[*pi].token != SL_PP_IDENTIFIER) {
+      strcpy(context->error_msg, "expected an identifier");
       return -1;
    }
 
@@ -172,6 +178,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
    if (!macro) {
       if (!mute) {
          if (sl_pp_process_out(state, &input[*pi])) {
+            strcpy(context->error_msg, "out of memory");
             return -1;
          }
       }
@@ -184,6 +191,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
    if (macro->num_args >= 0) {
       skip_whitespace(input, pi);
       if (input[*pi].token != SL_PP_LPAREN) {
+         strcpy(context->error_msg, "expected `('");
          return -1;
       }
       (*pi)++;
@@ -203,6 +211,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
 
          *pmacro = sl_pp_macro_new();
          if (!*pmacro) {
+            strcpy(context->error_msg, "out of memory");
             return -1;
          }
 
@@ -219,6 +228,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
                   if (j < (unsigned int)macro->num_args - 1) {
                      done = 1;
                   } else {
+                     strcpy(context->error_msg, "too many actual macro arguments");
                      return -1;
                   }
                } else {
@@ -236,6 +246,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
                   if (j == (unsigned int)macro->num_args - 1) {
                      done = 1;
                   } else {
+                     strcpy(context->error_msg, "too few actual macro arguments");
                      return -1;
                   }
                } else {
@@ -245,6 +256,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
                break;
 
             case SL_PP_EOF:
+               strcpy(context->error_msg, "too few actual macro arguments");
                return -1;
 
             default:
@@ -254,6 +266,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
 
          (**pmacro).body = malloc(sizeof(struct sl_pp_token_info) * body_len);
          if (!(**pmacro).body) {
+            strcpy(context->error_msg, "out of memory");
             return -1;
          }
 
@@ -301,6 +314,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
    if (macro->num_args == 0) {
       skip_whitespace(input, pi);
       if (input[*pi].token != SL_PP_RPAREN) {
+         strcpy(context->error_msg, "expected `)'");
          return -1;
       }
       (*pi)++;
@@ -310,6 +324,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
       switch (macro->body[j].token) {
       case SL_PP_NEWLINE:
          if (sl_pp_process_out(state, &macro->body[j])) {
+            strcpy(context->error_msg, "out of memory");
             return -1;
          }
          j++;
@@ -328,6 +343,7 @@ sl_pp_macro_expand(struct sl_pp_context *context,
       default:
          if (!mute) {
             if (sl_pp_process_out(state, &macro->body[j])) {
+               strcpy(context->error_msg, "out of memory");
                return -1;
             }
          }
diff --git a/src/glsl/pp/sl_pp_pragma.c b/src/glsl/pp/sl_pp_pragma.c
index 059bc6f2886..1cd9fd82348 100644
--- a/src/glsl/pp/sl_pp_pragma.c
+++ b/src/glsl/pp/sl_pp_pragma.c
@@ -99,6 +99,7 @@ sl_pp_process_pragma(struct sl_pp_context *context,
    /* Ignore the tokens that follow. */
 
    if (sl_pp_process_out(state, &out)) {
+      strcpy(context->error_msg, "out of memory");
       return -1;
    }
 
diff --git a/src/glsl/pp/sl_pp_version.c b/src/glsl/pp/sl_pp_version.c
index 82acdd1d5a4..6cd63f4925c 100644
--- a/src/glsl/pp/sl_pp_version.c
+++ b/src/glsl/pp/sl_pp_version.c
@@ -25,34 +25,10 @@
  * 
  **************************************************************************/
 
+#include <stdlib.h>
 #include "sl_pp_version.h"
 
 
-static int
-_parse_integer(const char *input,
-               unsigned int *number)
-{
-   unsigned int n = 0;
-
-   while (*input >= '0' && *input <= '9') {
-      if (n * 10 < n) {
-         /* Overflow. */
-         return -1;
-      }
-
-      n = n * 10 + (*input++ - '0');
-   }
-
-   if (*input != '\0') {
-      /* Invalid decimal number. */
-      return -1;
-   }
-
-   *number = n;
-   return 0;
-}
-
-
 int
 sl_pp_version(struct sl_pp_context *context,
               const struct sl_pp_token_info *input,
@@ -130,19 +106,9 @@ sl_pp_version(struct sl_pp_context *context,
             break;
 
          case SL_PP_NUMBER:
-            {
-               const char *num = sl_pp_context_cstr(context, input[i].data.number);
-
-               if (!num) {
-                  return -1;
-               }
-               if (_parse_integer(num, version)) {
-                  strcpy(context->error_msg, "expected version number after `#version'");
-                  return -1;
-               }
-               i++;
-               found_number = 1;
-            }
+            *version = atoi(sl_pp_context_cstr(context, input[i].data.number));
+            i++;
+            found_number = 1;
             break;
 
          default: